Question

1.Below are three statements. For each statement: (i) State whether the statement is true or false. (ii) Explain your reasoning.

A. In an additive relationship, Z defines a large compositional difference across values of X.

B. Field experiments have lower external validity than do laboratory experiments.

C. Random assignment neutralizes rival explanations.

Answer 1

A) false

in spurios relation , the control variable, Z, defines a large compositional differences across values of the independent variable, X. Further, this compositional difference is a cause of the dependent variable Y. After holding Z constant, the empirical association between X and Y turns out to be completely coincidental- not causal at all.

in additive relationship

the control variable is a cause of the dependent variable, but defines a small compositional difference across values of the independent variable. Because the relationship between X and Z is weak, X retains a causal relationship with Y after controlling for Z. In the additive scenario, the control variable, Z, also helps to explain the dependent variable.

b)

true

A lab experiment can be classed as having higher validity than a field experiment because a lab experiment gains control of all extraneous variables which could confound the results.

c)

true