For a two-factor design, describe what is meant by a main effect ...

[mikaylakyoung]

For a two-factor design, describe what is meant by a main effect and an interaction?
 
  What will be an ideal response?

Question 2

In contrast to many other experimental designs, the covariance design necessarily includes ____.
 
  a. randomization
 b. a pre-program measure
  c. a control group
 d. blinding

[bblaney]

Answer to Question 1

The overall mean differences among the levels of one factor are called the main effect for the factor. A two-factor study can be displayed as a matrix with the levels of one factor defining the rows and the levels of the other factor defining the columns. In this structure, the differences among the column means define the main effect for one factor and the differences among the row means define the other main effect. An interaction occurs when the differences among the individual treatment means (cells in the matrix) are not consistent with the overall differences among the corresponding rows or columns. An interaction means that the effect of one factor depends on the levels of the second factor.

Answer to Question 2

b

[mikaylakyoung]

Excellent

[patma1981]

Gracias!