Suppose you are interested in studying whether temperature affects spatial reasoning abilities. You decide to test spatial reasoning using completion time scores for the paper-folding test with five people, repeating the test on each person with three different temperatures (40 degrees, 60 degrees, and 80 degrees Fahrenheit). In this experiment, the null hypothesis is that:

a. There are no differences in the mean completion times among the temperatures compared
b. There are no individual differences in the completion time means
c. The completion time mean for at least one temperature is different from another

The factor of interest is the , and the dependent variable is the .