Why is it hard to make causal conclusions if an independent ...

[SO00]

Why is it hard to make causal conclusions if an independent variable involves a subject (or participant) variable?
 
  What will be an ideal response?

Question 2

Identify and describe the four types of independent variables according to type of manipulation.
 
  What will be an ideal response?

[kjo;oj]

Answer to Question 1

Subject or participant variables involve measurement of differences in behavior across groups that share categorization based on a measured variable. Because the differences are pre-existing, we can't assume that the people in different groups form equivalent groups at the outset; they aren't randomly assigned. As such, there may be variables that affect behavior that are associated with membership in that group; differences in behavior may not really be due to differences in the measured variable.

Answer to Question 2

(a) Task variableThe independent variable is set up so that participants in different conditions engage in different tasks.
(b) Instructional variableThe IV is set up so that participants in different conditions receive different instructions about what they are going to do.
(c) Situational variableThe IV is set up so that the context or setting of the experiment differs across groups.
(d) Subject variableThe IV is set up so that comparisons are made between two groups of people who differ in some pre-existing way (e.g., sex, political affiliation, etc.)

[SO00]

TYSM

[parshano]

Great answer, keep it coming