Download P290 - Hypotheses and Variables - 15

Psychology 290
Lab 3
September 28-30, 2015
• Hypotheses
• Variables
Hypotheses
• Predictions
– Predicted relationship
(with or without direction)
• Correlational
– Predicted difference
• Can be Causal
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
Variables Cont.
•
Other variables outside the focus of the study that may affect the results
•
Extraneous
– Unsystematic differences that affect the DV
– E.g.
•
Confounding
– Variables that change systematically with IV
•
Control
– Variables that are held constant
– E.g. researchers, experimental rooms, temperature …
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, Selfreport measures
Summary
• Hypothesis: What is being predicted?
– 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?
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.