1. Psychology 290 Lab 3 September 28-30, 2015
Hypotheses
Variables

2. Hypotheses Predictions Predicted relationship
(with or without direction)
Correlational
Predicted difference
Can be Causal

3. Variables Defined by Their Use
Measured
Variables that are assessed by the experimenter
Correlational vs. Differential studies
Classification variable
A pre-existing characteristic that the experimenter uses to categorize the participants
E.g. Grouping Ps. according to sex
Independent
Manipulated by the experimenter
E.g. Randomly assigning Ps. to receive placebo, low dose, or high dose
Dependent
Not under the control of the experimenter
The measured variable in an experiment
E.g. Reaction time

4. Variables Cont.
Other variables outside the focus of the study that may affect the results
Extraneous
Unsystematic differences that affect the DV
Confounding
Variables that change systematically with IV
Control
Variables that are held constant
E.g. researchers, experimental rooms, temperature …

5. Variables Defined by their Nature
Behavioural: Any observable response
E.g. A rat bar pressing for food pellets
Stimulus: Anything that acts on a P
E.g. A light to indicate a response is required
Organismic/Subject: A characteristic used to classify a P
Observed: Age, gender
Response Inferred: Racial attitudes, Self-report measures

6. Summary Hypothesis: What is being predicted? Measured Variables
When trying to identify the hypothesis look for key words such as:
Hypothesized
Objective
Investigate
Measured Variables
Assessed by the experimenter
Pre-existing characteristic or measured
The independent variable is manipulated.
IV: What did the researchers change in order to group participants?
The dependent variable is what changed as a result of the manipulation.
What were researchers trying to find/elicit a change in?
What was measured?
The control variable is held constant.
What factors did the experimenters hold constant across trials/groups?

7. A drug company is advertising a new drug that helps people recover from jet lag faster. You are skeptical, so you conduct an experiment to test their claim. In your experiment, 100 people are flown from San Francisco to Tokyo. During the flight, half of the participants are given the drug company’s new drug. The other half of the participants are given a placebo during the flight. Six hours after they land, all participants are asked to rate how sleepy and disoriented they feel.
What is the hypothesis?
What type of research design was used?
Identify all of the key variables examined and what type of variable is each one?
i.e. independent, dependent, mediating, control