LESSON ONE: TYPES OF EXPERIMENTSAIMS AND HYPOTHESES

Research methods

Types of Experiment

Laboratory Experiment

Field Experiment

Quasi or Natural Experiment

Research that uses the experimental method…

Study: Explanation of experimental method used:

Laboratory Experiment

There is high control of variables.The psychologist manipulates the IV, decides

where the experiment will take place, at what time and with which participants, in what circumstances, and using a standardised procedure.

This standardisation may create demand characteristics. These are features of the research which may affect participants behaviour, so they act unnaturally or look for cues to tell them what the research is about and behave accordingly

Laboratory Experiment

Strengths Weaknesses

Field Experiment

Psychologist manipulates the IV but the experiment takes place in a real life setting.

Less control over variables eg the people who take part or when the study happens.

Participants often (but not always) unaware that they are participating in a study.

E.g. Piliavin

Field Experiments

Strengths Weaknesses

What is a natural (quasi) experiment?

A study that takes place in a natural environment. However, the IV is not

being controlled. It is naturally occurring.

In St Helena, a study took place to see whether introducing TV would increase anti-social behaviour. The residents on the island

received TV for the first time in 1995. The vast majority of the measures used to assess pro

and anti social behaviour showed no differences in either.

Natural Experiments

Strengths Weaknesses

Enables psychologists to study ‘real’ problems such as the effects of disaster on health (increased ecological validity)

Cannot demonstrate causal relationships because IV not directly manipulated

Less chance of demand characteristics/social desirability.

Participants may be aware of being studied, reduces naturalness.

Can study things that it would be unethical to set up or manipulate.

If unware: ethical issues.

What is an Aim?

The aim of an investigation is its general purpose.

What are you trying to achieve in the investigation?

How do I write an AIM?

An aim should always start with ‘To investigate..’

Using common sense and your knowledge of psychology state two aims

appropriate to each of the research aims given below:

Using common sense and your knowledge of psychology state two aims

appropriate to each of the research aims given below:

Study 1: A study into the effect of alcohol on a person’s ability to drive a car.

Study 2: Are there gender differences in communication skills?

Students should work in pairs. One person (the participant) reads the word lists while the other person (the experimenter) needs to time how long it took to read each list (all mobile phones have timers)

Participants should state the colour of the word, not what the word says. For example, for the word ‘BLUE’ they should say ‘red’, for the word ‘BROWN’ they should say ‘brown’.

Participants should take great care to say the colour correctly and not race against the clock. Mistakes should be corrected.

Experimenter says ‘start’ to signal participant should begin reading the first list.

Participant says ‘stop’ at the end of the list, so the experimenter can record how long it took to read the list.

Practical Activity:

Let’s do an experiment…List 1

redblue

greenbrownpurplebluered

browngreen

redpurple

redblue

brownSTOP

The Stroop Task

Let’s do an experiment…

The Stroop Task

List 2

bluegreenpurple

redbrown

redblue

greenbrownpurplebrownpurple

redblueSTOP

RESULTS:

List 1 List 2

Total

Mean

What did we find?Plot our results on the graph below:

What did stroop find?

What is a Hypothesis?

A hypothesis states what you believe to be true.

It is a precise and testable statement of the relationship between two variables.

Participants who are older (measured in years and months will score more

highly on an IQ test.

What are the two main types of hypothesis?

The hypothesis is sometimes called the experimental hypothesis or the alternative hypothesis.

There is also a null hypothesis. A null hypothesis, says that there is no difference or no relationship between the variables.

There is no significant relationship between age (years) and intelligence (score on IQ

test).

What were our hypotheses?

We just conducted a stroop task. I would like you to write the aim, experimental hypothesis and the null hypothesis for our experiment.The Stroop Test

Aim

Hypothesis

Null Hypothesis

ONE OR TWO TAILED?

A directional (one-tailed) hypothesis states the kind of difference or relationship between the two variables.

A non-directional (two-tailed) hypothesis simply predicts that there will be a difference or relationship between the two conditions/variables.

If you are predicting

in one direction it’s one-tailed.

If you are predicting a change

either way: two-

tailed.

Plenary – mark in the box and hold your iPad up

For each of the following, decide whether it is a directional or a non-directional hypothesis:

Select which type of hypothesis: One-tailed

Two-tailed

Boys and girls will score differently on aggressiveness tests.

Hamsters are better pets than budgies.

People remember more of the words that appear early in a list than the words that appear later.

Students who have a computer at home get better grades in exams than those who do not.

Extension: write your own idea for a hypothesis

LESSON TWO: VARIABLES

Research methods

Starter:

For each of the following please identify the IV and DV.

There is a difference in the speed with which people react to visual and auditory stimuli.

Drug A affects memory

First children learn to speak earlier than subsequent children.

Ext: Write an aim for the hypothesis.

Variables

Independent variable: is the one that is

changed.

Dependent variable: the one that is measured.

Let’s do an experiment

We are going to do an experiment which involves two conditions. One where the participants will do a test with no music and another condition where the students have to listen to music to

do the test.

What is the aim of our study?Write a non-directional hypothesis for this study?Write a one-tailed hypothesis for this research?

What is the IV?What is the DV?

The noise experiment

Does noise affect your performance on a memory task?

The variable we are going to change (the IV) is noise (music/no music) The variable we are going to measure (the DV) is performance (no. of

words recalled) on a memory task. You will need a radio (youtube) and two lists of 20 words each. Divide your class in half: Group N (noise) and Group S (silent). Group N should have the radio playing very loudly when they are shown

the list of words. They have 1 minute to try to remember them and then one minute to write them down.

Group S should do the same task in silence with the second list of words

We need:An independent experimenter to time one minuteMusicTable to record results

Condition 1 – without noise

Condition 2 – with noise

Results

Which group did better in the test?

Condition 1 (without noise)

Condition 2 (with noise)

Total

Range

Mean

Median

Mode

Measures of central tendency Mean: Add

values, divide by number of values

Median: Middle value in an

ordered list

Mode: The most common value(s)

Measures of dispersionRange Highest to lowest

Standard Deviation

Mathematical calculation

An extraneous variable is a variable other than the IV that may affect the DV and should be controlled.

An extraneous variable is also called a confounding variable.

Possible extraneous variable

Effect it may have had

1. Situational variables are characteristics of the environment in which the experiment is being conducted which may have an effect on the results. The nature of these variables is very much dependent on the nature of the experiment but temperature, time and humidity could all be situational variables.

2. Person or Subject variables are inherent characteristics of the Experimental Unit that might affect outcomes. Hence examples of subject variables might include age, gender and other demographic details (among subjects) and x, y and z (among objects) although this is very much dependent on the object in the experiment.

3. Experimental variables are characteristics of the experimenter or the experimental team which might influence how the experiment is conducted, or how the experimental subject responds/behaves in the experimental setting. There is a wide definition for these variables and they may include age, gender, qualifications, etc.

One last extraneous variable

The behaviour of the investigator may affect the experiment and, therefore, the DV.

For example, the way the investigator asks a question may lead the participant to give the answer the participant wants. Or simply the experimenter may encourage certain kinds of response (these are called demand characteristics!)

Control of investigator effectsAnything that investigator does which has an effect on the participant’s performance other than what was intended

Single blind

Double blind

Placebo conditions

Standardised instruction

s

LESSON THREE: EXPERIMENTS AND EXPERIMENTAL DESIGN

Research methods

What is an experiment?

An experiment is a way of conducting research where:

One variable is changed (the IV) and the effects are measured (the DV)

Controlled environmentStandardised procedure

Experimental design

There are 3 main types of experimental design:Independent groupsRepeated measuresMatched pairs

Independent Groups

Repeated measures

Matched Pairs

Each participant is tested in only one condition. There are two (or more) separate groups of participants.

Each participant is tested in both conditions. They would be tested in all conditions in a certain order.It involves independent groups, but each pp in group 1 is paired with a pp in group 2. This is done by matching key variables such as IQ, age and gender.

Advantages

Independent Groups

Repeated Measures

Matched Pairs

Disadvantages

Independent Groups

Repeated Measures

Matched Pairs

What are the advantages of an experiment?

What are the disadvantages of an experiment?

Quiz1. The independent variable in a study is…a. The one that is excluded.b. The one that is manipulated by the experimenter.c. The one that is observed or measured.d. Not of interest to the experimenter.

2. Which of the following hypotheses is a non-directional hypothesis?

a. Participants in the no noise condition do better on the memory test than those in the noise condition.

b. Participants who drink alcohol have a slower reaction time than those who have no alcohol.

c. Participants like words that are familiar better than those that are not familiar.

d. Participants who expect to perform better perform differently from those given lower expectations.

3. One reason for using a directional hypothesis would be because…

a. Past research suggests that participants will do better on one condition than another.

b. Past research is uncertain about how participants will perform.c. There is no past research.d. The researcher wants to make a strong statement.

4. An extraneous variable is a variable that… a. Has been controlled by the experimenter.b. Confounds the findings of the study.c. May influence the dependent variable.d. The experimenter wants to find out more about.

5. A student plans to investigate the effects of practice on IQ test performance. Some participants are given two practice tests prior to the IQ test whereas others do no test beforehand. The dependent variable in this study is…

a. The participants.b. The effects of practice.c. IQ test performance before the study.d. IQ test performance at the end of the study.

6. The study described in question 6 above is a…a. A Repeated measures design.b. A Independent groups design.c. A Matched pairs design.d. A Careful design.

7. In an independent groups design…a. There are two or more separate groups of participants.b. The analysis involves comparing measures from two or

more separate groups of people. c. The analysis involves comparing two measures from the

same person.d. Both a and b

8. One advantage of doing a matched pairs design is…

a. You need fewer participants than for repeated measures.b. You can control some participant variables.c. Order effects are not a problem.d. Both b and c

9. Which of the following could not be an extraneous variable in a study…

a. An investigator effect.b. A confederate.c. An order effect.d. Lack of standardised procedures.

10. Which of the following is a disadvantage of using a repeated measures design?

a. It does not control participant variables.b. You have to use more participants than for independent groups

design.c. There are more likely to be investigator effects than for independent

groups design.d. There may be order effects

Example Exam Questions:

January 2013 Psychologists wanted to investigate if the colour of food influenced how it tasted. To

do this they made two bowls of mashed potato. One was normal creamy white in appearance, whereas the other had a green tasteless and odourless food colouring added. Each participant had to taste both the normal and green potato and rate how much they liked each one using a scale of 1 (don’t like it at all) to 10 (like it a lot).

1 a) Identify the experimental design used in this study. b) Outline one strength and one weakness of using the experimental design in this study.

(6) 2. Identify the IV and DV in this study. (2)3. Describe and evaluate one other way to measure the DV in this study. (10)

Homework:

January 2011A. Identify the experimental design used in this study. (2)B. Outline one strength and one weakness of using this

experimental design in this study. (6)2. Identify the IV and DV in this study. (2)3. Describe and evaluate one other way to measure the

DV in this study. (10)