11/6; 11/11: MANIPULATING INDEPENDENT VARIABLE/EXPERIMENTER BIAS

I. Manipulating Independent variables

A. Setting the stage--cover stories

1. deception

a. omission

b. commission

B. Manipulation check

C. types of manipulations

1. social

2. environmental

3. instructional

II. Experimenter effects

A. Unintentional effects

1. No effects on the participants

a. observer effects

b. often biased in direction of the hypothesis

c. solutions

1. double check data

2. keep observers blind to hypotheses

2. Interpreter effects

a. science is not completely objective

b. this is a detectable effect, observer effects are not

c. confirmatory bias

B. Effects that influence the participants’ behavior

1. attributes of the experimenter, eg., gender, warmth

2. modeling effects--tendency for experimenters to get the data from participants that they themselves would have given

3. experimenter expectancy effects--may come to elicit the effects they expect because they treat participants differently

a. Pygmalian in the classroom

b. animal studies

4. controlling for experimenter expectancy effects

a. increase the number of experimenters

b. observe the behavior of the experimenters

c. train experimenters carefully

d. minimize experimenter-participant contact

e. keep experimenters blind to hypotheses and/or conditions