Question

1. Write an appropriate model for the research question(s).
2. Specify the appropriate null and alternative hypotheses for the research question(s).

1. In an experiment each participant solves one of two types of problems (spatial or verbal) at one of three levels of difficulty (easy, moderate, or hard). Half of the 60 participants are given instructions to use visual imagery, and half are told to use subvocalization. The dependent variable is the number of eye movements per second that a participant makes while working on a problem. The researchers want to know the type of problem and level of difficulty have an interaction effect on the dependent variable.

Answer 1

We have two factors here which are Type of Problem (two levels) and Level of difficulty (three levels). Hence, the appropriate model here is Two Factor Factorial experiment (3x2)

The model is:

Mu is the grand mean

Alpha is the effect of Type of Problem

Beta is the effect of level of difficulty

Gamma is the interaction effect

i and j are the levels of the factors

The appropriate hypotheses are:

Ho: γ_ij = 0, for all i,j

Ha: γ_ij =/ 0 for atleast one pair