Interpreting Communication Research Chapter 2 Laboratory Experimental Research By Frey, Botan, Friedman, & Kreps

Experiments compare groups of people Experiments attempt to discover causal principles Experiments investigate whether one variable causes another variable to change Changes in the dependent variable must be shown to be the result of changes in the independent variable and not due to some other variable(s) The researcher must rule out competing explanations for changes in the dependent variable (extraneous or confounding variables) Experimental Research Overview

Types of Experiments Full (true) Experiments –maximum amount of control Laboratory Experiments –take place in a setting created by the researcher Field Experiments –take place in a natural environment Quasi-Experiments –moderate control Pre-Experiments –little or no control

Factorial Experiments Experiments that study the effects of two or more independent variables are called factorial experiments Factorial experiments tell us 2 things: (1) the effects of each independent variable (called main effects), and (2) the effects of the independent variables working together (called an interaction effect)

EXERCISING A HIGH DEGREE OF CONTROL (1) MANIPULATING AN INDEPENDENT VARIABLE (2) RANDOMLY ASSIGNING SUBJECTS TO EXPERIMENTAL CONDITIONS (3) ACCOUNTING FOR THE INFLUENCE OF EXTRANEOUS VARIABLES

Questions for Examining Full Experimental Research Let’s look at pages Are the hypotheses clearly stated? Was the manipulation of the independent variables successful? How well did the researcher do in controlling for extraneous variables?

Anticipated Interaction and Information Seeking

Review of Douglas’ study, “Anticipated Interaction and Information Seeking” We’ll break up into small groups (say, 3 people per group) and each group will summarize Douglas’ study. Write down the summary. And each group will present their summary to the whole class.

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