Calebs 2013 Stats Lecture 3

7/30/2019 Calebs 2013 Stats Lecture 3

1/39

Outline and readings for Lecture 3

Key topics addressed

*Anecdotal evidence and its problems

*Correlation*Independent and Dependent Variables

*Types of research design: Correlational, Quasi-Experiment, True Experiment

*External Validity

*Internal Validity

*The need for a control condition

*Blinding

Recommended reading:* Taylor, James. Efficacy and safety of Echinacea in treating upper respiratory tract infections in children: A

randomized controlled trial.

PDF is on library website, direct link is:http://opac.library.usyd.edu.au/search~S4?/rpsyc1001/rpsyc1001/1,1,1,B/frameset~3140013&FF=rpsyc1001&1,1,

NB: If this link or any other library article link does not work, go to the library website: http://www.library.usyd.edu.au/

Then CATALOGUE, select Unit of Study, and type in PSYC1001. You will find a page of articles and this one will be one of them.

Recommended media:

Enemies of Reason BBC 2008 download from Blackboard (from the front page Videos related to

Psychology lectures and tutorials). It is 44minutes for this lecture it is the section on Dowsing which will

be specifically referred to 24:40 29:40.
http://opac.library.usyd.edu.au/search~S4?/rpsyc1001/rpsyc1001/1,1,1,B/frameset~3140013&FF=rpsyc1001&1,1http://www.library.usyd.edu.au/http://www.library.usyd.edu.au/http://opac.library.usyd.edu.au/search~S4?/rpsyc1001/rpsyc1001/1,1,1,B/frameset~3140013&FF=rpsyc1001&1,1


2/39

Science & Statistics in Psychology

Lecture 3

A thousand zeros is still nothing

Dr Caleb Owens


3/39

Lecture Outline

Research designsAnecdotes and case studies Correlational studies

Quasi-experiments

True experiments

External validity

Random sampling

Internal validity Random allocation

Blinding

Even more terminology Independent

variable

Dependent variable Control condition


4/39

Baby got sick anecdote

Hypotheses:Change in formula

Virus

Change in weather

Local water supply

Teething

Requires solids

Important points:Anecdote may only contain

one possible cause

What advice would I give to

other parents and how would I

qualify that advice?


5/39

Condition ParticipantParticipant Participant Participant Participant Participant Participant Participant

No change

in formula

1 2 3 4 5 6 7 8

Aust

Formula ->Japan

Formula

9 10 11 12 13 14 15 16

Japan

Formula ->

Aust

Formula

17 18 19 20 21 22 23 24

24 babies (8 per condition) needed for a controlled test of just ONE

hypothesis

Why would we think that our observations of ONE baby would be

enough to distinguish between SIX plausible hypotheses?


6/39

Anecdotal evidence

The plural of anecdote is not evidence

Anecdotes are usually worse than useless

Because they generally support what we believe

The anecdote contains the (proposed) explanationwhich cannot be untangled once it is passed on

It cannot be replicated or documented by non-

prejudiced observers

It changes with every retelling and depends on falliblememory

At most anecdotes provide clues and leads


7/39

I got better anecdote

I am living proof that X works

I had illness Y, and was treated with X, and then

I got better!

So it must have been X !!!

What is wrong with this conclusion?

What else could have happened?


8/39

Case studies

Significantly more systematic than anecdotes All details taken and recorded in a scientific manner

May simply consist of the combination of previouslycollected information

Can consist of the systematic collection of longitudinaldata E.g. The famous television series: 7-up, 49-up

Provide important details which can lead to latersystematic research and breakthroughs

Should not be over-interpreted since the sample size isoften small and rarely randomly selected Ideal for investigating rare or highly specific topics

E.g. prosopagnosia


9/39

Anecdote

My Aunty Liz got Cholera fromthe terrible smells and gases

coming from the river near herhouse. She moved house.Whenever she smellssomething bad from now onshe stays away and hasnt gotCholera since!

Case Study

Elizabeth Cromwell contractedCholera on 12th July 1723

during a particularly hotsummer.

When winds were blowingfrom the East, her housebecame filled with noxiousgases causing a terrible smell.

She was an otherwise healthywomen whose only otheraffliction was mild Dysenterysome years earlier.

Her house was located next tothe river Thames which at thetime contained a large amountof raw sewage.

She drew her drinking waterfrom a well which was exposedto the river.


10/39

Correlational studies

Measure two naturally occurring variables Find a relationship between them

Only a very weak causal inference could

be drawn (a suggestion, a lead for moreresearch)

No independent variables are controlled

e.g. Simply look through lots of data and find

relationships


11/39

Correlation Coefficients

XY = 0.7

The sign (+ or ) indicates

the direction of the

relationship(+ : as values on one variable get bigger,values on the other get bigger; - : as values

on one variable get bigger, values on the

other get smaller)

The number indicates

the strength of the

relationship(0.1, 0.2, 0.3 = weak ;

0.7, 0.8, 0.9 = strong)


12/39

Scatterplots

X

100806040200

Y

600

400

200

0

-200

-400

-600

X

100806040200

Y

120

100

80

60

40

20

0

-20

XY = 0.25

XY = 0.88Positive Correlations

The score on two

IQ tests taken on

the same day

The relationshipbetween High

School grades

and University

grades

Each person has two scores and these

are plotted on separate axes


13/39

Scatterplots

X

100806040200

Y

20

0

-20

-40

-60

-80

-100

XY = -0.93

X

100806040200

Y

400

300

200

100

0

-100

-200

-300

-400

XY = -0.16

Negative Correlations

The number of

hours of exercise

people do and their

excess fat in a

pinch test

The amount of

time people

spend on the

internet and their

university grades


14/39

Correlation and Causation

Just because two variables are correlated

with each other does not mean that one

causes the other.

Example: The number of ice-creams

consumed on a certain day correlates

positively with deaths by drowning (0.8)


15/39


It could be that:

Eating ice-cream causes drowning

Drowning causes ice-cream to be eaten

Amount of ice-cream eaten and number ofdrownings are both caused by the

temperature on a particular day

Does the cold of winter cause colds andflu ?

http://www.straightdope.com/columns/read/997/why-is-winter-the-season-for-colds-flu-etc
http://www.straightdope.com/columns/read/997/why-is-winter-the-season-for-colds-flu-etchttp://www.straightdope.com/columns/read/997/why-is-winter-the-season-for-colds-flu-etchttp://www.straightdope.com/columns/read/997/why-is-winter-the-season-for-colds-flu-etchttp://www.straightdope.com/columns/read/997/why-is-winter-the-season-for-colds-flu-etchttp://www.straightdope.com/columns/read/997/why-is-winter-the-season-for-colds-flu-etchttp://www.straightdope.com/columns/read/997/why-is-winter-the-season-for-colds-flu-etchttp://www.straightdope.com/columns/read/997/why-is-winter-the-season-for-colds-flu-etchttp://www.straightdope.com/columns/read/997/why-is-winter-the-season-for-colds-flu-etchttp://www.straightdope.com/columns/read/997/why-is-winter-the-season-for-colds-flu-etchttp://www.straightdope.com/columns/read/997/why-is-winter-the-season-for-colds-flu-etchttp://www.straightdope.com/columns/read/997/why-is-winter-the-season-for-colds-flu-etchttp://www.straightdope.com/columns/read/997/why-is-winter-the-season-for-colds-flu-etchttp://www.straightdope.com/columns/read/997/why-is-winter-the-season-for-colds-flu-etchttp://www.straightdope.com/columns/read/997/why-is-winter-the-season-for-colds-flu-etchttp://www.straightdope.com/columns/read/997/why-is-winter-the-season-for-colds-flu-etchttp://www.straightdope.com/columns/read/997/why-is-winter-the-season-for-colds-flu-etchttp://www.straightdope.com/columns/read/997/why-is-winter-the-season-for-colds-flu-etchttp://www.straightdope.com/columns/read/997/why-is-winter-the-season-for-colds-flu-etc


16/39

Some plausible correlational findings

Living close to the beach is correlated with being rich Causation in the other direction ?

Religiousness is correlated with being on death row Causation in the other direction ? Third variable ?

Arriving illegally by boat is correlated with being violent Third variable ?

Being at University is correlated with being homosexual Measurement bias ?

Height is correlated with IQ Third variable ?


17/39


In general, if A & B are correlated it ispossible that:

A causes B

B causes A

Some other variable C causes both A & B

Correlation Causation!


18/39

http://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_u

pshot/mcdonalds-happy-meal-resis

ts-decomposition-for-six-months
http://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-monthshttp://news.yahoo.com/s/yblog_upshot/20101012/bs_yblog_upshot/mcdonalds-happy-meal-resists-decomposition-for-six-months


19/39

http://www.n

aturalnews.com/030074_H

appy_Meal_decompose.html
http://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.htmlhttp://www.naturalnews.com/030074_Happy_Meal_decompose.html


20/39

Source:http://aht.seriouseats.com/archives/2010/11/the-burger-lab-revisiting-the-myth-of-the-12-year-old-burger-testing-results.html
http://aht.seriouseats.com/archives/2010/11/the-burger-lab-revisiting-the-myth-of-the-12-year-old-burger-testing-results.htmlhttp://aht.seriouseats.com/archives/2010/11/the-burger-lab-revisiting-the-myth-of-the-12-year-old-burger-testing-results.htmlhttp://aht.seriouseats.com/archives/2010/11/the-burger-lab-revisiting-the-myth-of-the-12-year-old-burger-testing-results.htmlhttp://aht.seriouseats.com/archives/2010/11/the-burger-lab-revisiting-the-myth-of-the-12-year-old-burger-testing-results.htmlhttp://aht.seriouseats.com/archives/2010/11/the-burger-lab-revisiting-the-myth-of-the-12-year-old-burger-testing-results.htmlhttp://aht.seriouseats.com/archives/2010/11/the-burger-lab-revisiting-the-myth-of-the-12-year-old-burger-testing-results.htmlhttp://aht.seriouseats.com/archives/2010/11/the-burger-lab-revisiting-the-myth-of-the-12-year-old-burger-testing-results.htmlhttp://aht.seriouseats.com/archives/2010/11/the-burger-lab-revisiting-the-myth-of-the-12-year-old-burger-testing-results.htmlhttp://aht.seriouseats.com/archives/2010/11/the-burger-lab-revisiting-the-myth-of-the-12-year-old-burger-testing-results.htmlhttp://aht.seriouseats.com/archives/2010/11/the-burger-lab-revisiting-the-myth-of-the-12-year-old-burger-testing-results.htmlhttp://aht.seriouseats.com/archives/2010/11/the-burger-lab-revisiting-the-myth-of-the-12-year-old-burger-testing-results.htmlhttp://aht.seriouseats.com/archives/2010/11/the-burger-lab-revisiting-the-myth-of-the-12-year-old-burger-testing-results.htmlhttp://aht.seriouseats.com/archives/2010/11/the-burger-lab-revisiting-the-myth-of-the-12-year-old-burger-testing-results.htmlhttp://aht.seriouseats.com/archives/2010/11/the-burger-lab-revisiting-the-myth-of-the-12-year-old-burger-testing-results.htmlhttp://aht.seriouseats.com/archives/2010/11/the-burger-lab-revisiting-the-myth-of-the-12-year-old-burger-testing-results.htmlhttp://aht.seriouseats.com/archives/2010/11/the-burger-lab-revisiting-the-myth-of-the-12-year-old-burger-testing-results.htmlhttp://aht.seriouseats.com/archives/2010/11/the-burger-lab-revisiting-the-myth-of-the-12-year-old-burger-testing-results.htmlhttp://aht.seriouseats.com/archives/2010/11/the-burger-lab-revisiting-the-myth-of-the-12-year-old-burger-testing-results.htmlhttp://aht.seriouseats.com/archives/2010/11/the-burger-lab-revisiting-the-myth-of-the-12-year-old-burger-testing-results.htmlhttp://aht.seriouseats.com/archives/2010/11/the-burger-lab-revisiting-the-myth-of-the-12-year-old-burger-testing-results.htmlhttp://aht.seriouseats.com/archives/2010/11/the-burger-lab-revisiting-the-myth-of-the-12-year-old-burger-testing-results.htmlhttp://aht.seriouseats.com/archives/2010/11/the-burger-lab-revisiting-the-myth-of-the-12-year-old-burger-testing-results.htmlhttp://aht.seriouseats.com/archives/2010/11/the-burger-lab-revisiting-the-myth-of-the-12-year-old-burger-testing-results.htmlhttp://aht.seriouseats.com/archives/2010/11/the-burger-lab-revisiting-the-myth-of-the-12-year-old-burger-testing-results.htmlhttp://aht.seriouseats.com/archives/2010/11/the-burger-lab-revisiting-the-myth-of-the-12-year-old-burger-testing-results.htmlhttp://aht.seriouseats.com/archives/2010/11/the-burger-lab-revisiting-the-myth-of-the-12-year-old-burger-testing-results.htmlhttp://aht.seriouseats.com/archives/2010/11/the-burger-lab-revisiting-the-myth-of-the-12-year-old-burger-testing-results.htmlhttp://aht.seriouseats.com/archives/2010/11/the-burger-lab-revisiting-the-myth-of-the-12-year-old-burger-testing-results.html


21/39

The control condition

Since variables change (or do not change)all by themselves, or by the action of

unforeseen agents, a no-manipulation, no-

drug, unaffected, control condition isneeded

This is usually one level of a manipulated

independent variable Condition 1: Drug High Strength

Condition 2: Drug Low Strength

Control Condition 3: No drug


22/39

Independent & Dependent

Variables

Presumed Cause

Antecedent Cause

Stimulus Variable

Behaviour of Interest

Response Variable

Independent

Variable

Dependent

Variable

Manipulated by

experimenterMeasured by

experimenter


23/39

Correlational studies

Measure two naturally occurring variables Find a relationship between them

Only a very weak causal inference could

be drawn (a suggestion, a lead for moreresearch)

No independent variables are controlled

e.g. Simply look through lots of data and find

relationships


24/39

True Experiments Randomly allocate subjects to different levels of the

independent variable

So all independent variables of interest are controlled

By not letting subjects choose, most confounds

cancel each other out because you have a randomamount of each in each group

E.g. When subjects turn up you toss a coin to see which

condition they go into. If the experiment is based on speed,then with enough subjects, naturally fast and slow people

in each condition will cancel each other out


25/39

Quasi-experiments Some attempt at controlling variables

Matching Manipulating some IVs but not others

Always a study of pre-existing groups in some sense

Whenever you have pre-existing groups you have

obvious confounds

Causal inference is weak

Example

When studying the psychological impact of domesticviolence, you find a control group which has not

experienced violence (and you want to ensure the groups

are as similar as possible), and you may give both groups

different kinds of therapy


26/39

Random allocation of independent

variables

Correlational study : NONE

Quasi experiment : At least one (but not

others); or none, but some attempt to

control one (e.g. matching)

True Experiment : ALL


27/39

Research Designs: Drug use example

Correlational: simply record the amount of alcoholconsumed and University Grades Weak causal inference

Numerous alternative explanations

Quasi-experimental: Select a group of people whodrink regularly and a group who do not, match themon diet, exercise, age and lifestyle and compare theirgrades Eliminates some confounds

Does not control for all variables (e.g. attitude, personality) True experiment: Randomly allocate 250 people to

drink heavily and 250 to drink a placebo control Controls for most extraneous variables

Puts 50% at risk !


28/39

Research Designs: Self-Esteem Example

Correlational: Record self-esteem and University

Grades and look for a relationship Weak causal inference

Numerous alternative explanations

Quasi-experiment: take people who have high self-

esteem and low self-esteem; compare their gradesand try to improve these with extra classes or peersupport Eliminates some alternative explanations

Self-esteem is still pre-existing and may have been caused

by a third variable True experiment: Randomly allocate 250 people to

high self-esteem and 250 people to low self-esteemand measure the impact on Uni grades Controls for most extraneous variables

Impractical, unethical


29/39

Control means:

Being able to determine what level of the

independent variable(s) any participant willreceive

There is no control when: Participants self-select which group they are

in (e.g. Choosing a particular treatment)

Participants already belong to a level of theindependent variable because of a pre-

existing condition

The independent variable cannot be easily or

ethically changed


30/39

Controlling variables

Hard to randomly

allocate:

Treatments

Lifestyles

Education

Experience

Diet

Impossible to randomlyallocate Sex

Brain damage (in humans)*

Psychological disorders Extreme stress / trauma

/anxiety

Sexuality

Family

Location Religion

Race

Income

*TMS, transcranial magnetic stimulation, now makes this possible


31/39

Sex differences

Males are better than females at spatial tasks(e.g. mental rotation)

Hypothesize: Maybe this is caused by males

having more experience with spatial toys

Match males & females on Lego experience

This is called holding the variable constant: its not the

same as the control you have in a true experiment

Males are better than females at spatial tasks but

when we controlled for spatial task experience the

difference disappeared


32/39

External validity

Based on sample size, and the representativeness ofthe sample and where and how the experiment isconducted

Depends on random selection of subjects and howclosely the setting matches the real world

How applicable is the data to the real world? How applicable to the real world are laboratory based

findings?

How well can you generalize from your results tothe real world? NB: This depends heavily on the topic


33/39

Internal validity

The ability to draw a causal inference

The extent to which changes in the DV are

likely to be due to changes in the IV

Depends on random allocation of subjects to

different levels of the IV and the elimination of

alternative explanations and confounding

variables Type of Research Design Internal ValidityCase Study / Anecdote Zero

Correlational Study Very low or zero

Quasi-Experiment Low to moderate

True Experiment High

Bli d


34/39

Blindness Being blind means you do not know what

treatment/condition is being administered

If the researcher is not blind May not randomly allocate correctly

May unconsciously change data

May unconsciously record data and affect outcome

If the subject is not blind The effect arises because they expect it to (placebo effect)

If both subject and experimenter dont know whatcondition is being administered it is called double-blind

Could anecdotal evidence ever be of a randomized

double blind nature?

Unblinded


35/39

Unblinded

Participant takes a pill knowing that it is intended to

relieve pain

Single-blind Participant is given a pill by a researcher (who knows

what it does) but is not told whether or not it will

relieve pain

Double-blind Researcher 1 makes the pills Yellow and Blue. She

gives them to Researcher 2 who does not know which

one has an active ingredient. Researcher 2 gives the

participant one of the pills and records how effective itis. Researcher 1 takes the data which records how

effective the Yellow and Blue pills were and makes a

conclusion (only they knew that the Blue pill

contained an active ingredient)


36/39

Clever Hans

-see http://en.wikipedia.org/wiki/Clever_hans


37/39

Dowsing: the ideomotoreffectSee video: Enemies of Reason Episode 1, 24:40-29:40

Download from Blackboard


38/39

Replication

Beyond the design, replication is everything inscience

Replication means the same findings can be foundagain by repeating the study

This is why in an APA formatted research article the Methodsection goes into enough detail to repeat the study

Beware of people and websites who pick out just ahandful of (often older) articles to support their view,

and ignore the fact such results were never foundagain, or are found very rarely (indicating a result dueto chance or bias)

Beware of groups who insist their results can only bereplicated by people who are trained in doing what

they do


39/39

Summary

Be able to distinguish between and define theseresearch designs: Case-study

Correlational study

Quasi Experiment True Experiment

Understand this important terminology External Validity

Random Selection Internal Validity

Random Allocation

Replication

Calebs 2013 Stats Lecture 3

Documents

Transcript of Calebs 2013 Stats Lecture 3