Quick Pre-AssessmentFor these questions, refer to the situation described below:

In an experiment designed to determine whether watching violent scenes on television increases the frequency of aggressive behavior in children, one group of subjects saw a nonviolent cartoon and another group saw a violent cartoon. In the play period that followed the viewing of the cartoons, researchers observed the two groups of children together and counted instances of aggressive behavior.

Taken from the 1994 released AP exam

1. The control group in the experiment is the group that

a. The researchers thought would be most aggressiveb. Performed the larger number of aggressive actsc. Performed the smaller number of aggressive actsd. Watched the violent cartoone. Watched the nonviolent cartoon

Quick Pre-AssessmentFor these questions, refer to the situation described below:

In an experiment designed to determine whether watching violent scenes on television increases the frequency of aggressive behavior in children, one group of subjects saw a nonviolent cartoon and another group saw a violent cartoon. In the play period that followed the viewing of the cartoons, researchers observed the two groups of children together and counted instances of aggressive behavior.

Taken from the 1994 released AP exam

• 2. The dependent variable in the experiment is the

a. Amount of aggressive behavior exhibited by the childrenb. Amount of time that each child spent interacting with the other

childrenc. Group in which each child was originally placedd. Violent cartoone. Nonviolent cartoon

Experimentation

• Aim is to control something that correlation or descriptive can’t

– Control = statistically remove differences

1. Manipulate the factors of interest2. Hold constant (control) factors to determine causal

relationship

• If a behavior changes when we vary an experimental factor, then we infer the factor is having an effect

– Experiments manipulate factors to determine its effect

Experimental research

• We want to find out how X affects Y

• X = a condition or event that varies in order to see impact on the other variable (controls)– INDEPENDENT VARIABLE

• Y = affected by the manipulation of the independent variable (usually measurement of the observed behavior)– DEPENDENT VARIABLE

Independent Variable – Misery Loves Company (need for affiliation)

• The thing the experimenter manipulates• In this scenario – IV = the________________

– Subjects were going to receive electric shocks– Group 1 was told the shocks would be high (creating HIGH

levels of anxiety)– Group 2 was told the shocks would be mild and painless

(creating LOW levels of anxiety)

• reality of the experiment: neither side would receive any shocks. – Deception is often necessary for experiments

And then…

Dependent Variable – Misery Loves Company (need for affiliation)

• The thing being measured• The participants desire to wait alone in the

company of others

Let’s Break it Down…

Experimental Group

• Special treatment in regard to the IV

Control Group

• No special treatment

**super important that BOTH groups be the same to avoid testing bias

How do we make it the same?

Extraneous Variables toConfounding Variables

• Other variables that seem likely to influence the DV in a specific study, and when they do, the extraneous variable becomes a confounding variable

• In this experiment: the sociability of the groups

Confounding Variables

• When 2 variables link together in a way that makes it hard to sort specific results– Researchers can’t tell which variable is having an

effect on the dependent variable• Misery Loves Company:

– Sociability of subjects is an extraneous variable that may alter the experiment to lead to a failed conclusion

Random Assignment

• Safeguards against possible confounding variables by all subjects having an equal chance of being assigned to any group or condition

Randomness – survey or experiment?

• Random sample = a good survey• Random assignment = a good experiment

MISCONCEPTION ALERT

• Psychology relies on RANDOM ASSIGNMENT for experiments, not RANDOM SAMPLING

• Random sampling is used on rare occasions for convenience – – Not representative for proper conclusion in

experimentation, unless paired with assignment to increase likelihoods

Variations on Designing Experiments – The Typing Experiment

1. Sometimes advantageous to use one group as both control and experiment group

• Referred to as “in-subject design”• Ex: effects of loud music on typing ability

Variations on Designing Experiments – The Typing Experiment

2. Sometimes you manipulate more than one IV– Ex: temperature in room and volume of music in

typing study– Interaction: effects of one variable depends on

effect of the other• In this case – does the loud must have a greater

effect on the typing ability if the temperature in the room is hotter or colder?

Variations on Designing Experiments – The Typing Experiment

3. Sometimes you have more than one DV– Ex: you look for speed AND accuracy in typing

experiment

Advantages/Disadvantages of Experimental Research

Advantages:• Cause/effect relationships (supposed

causation)

Disadvantages:• Oversimplification of reality, contrived

situations • Ethics (ex: experiment with pregnant women

and diets to see effect in birth weights)