Research methods part 1. ch.10 Experiment Basics

What is an experiment

At least 1 variable is manipulated and measured

Experimental variables

1. Independent/ Explanatory variable

2. Dependent/ Response variable

3. Control Variable

Independent Variable

what is manipulated

Dependent Variable

controlled by the researcher

Controlled Variable

what an experimenter holds constant in their study

Experiments Establish —-Covariance

Do the independent and dependent variables relate to one another?

How to establish covariance

You have to manipulate the independent variable so that you have at least 2 comparison groups

One type of comparison group (Covariance) — Control group

A neutral condition in which the participants experience no “treatment”

One type of comparison group (covariance) —-Placebo Groups

Receives an inactive treatment (like a sugar pill) to assess the placebo effect

Experiments Establish —- Temporal Precedence

Does the cause variable (independent variable) come first and the effect variable (dependent variable) come second?

How to establish Temporal precedence

when you manipulate the Ind. var. and observe the effects of the dep. var.

Experiments Establish —- Internal Validity

The causal variable (ind. var.) and not other factors is responsible for the change in the effect variable (dep. var)

(Internal Validity) Design Confounds

Alternative explanations for study results due to poor experimental design, severely threaten internal validity

Experiments Establish (internal validity)— Selection Effects

Kinds of participants in one level of Ind. Var. are systematically different from those in the other

Experiments Establish (Internal validity) —- to avoid selection effects, use

random assignment or matched groups