Within-Ss ANOVA Practice Questions Initialize R by entering the following commands at the prompt:

1. An experiment was conducted to measure the effect of practice on visual contrast sensitivity. Detection threshold was measured on four consecutive days for eight subjects. The dependent variable was contrast sensitivity, which was defined as the reciprocal of the minimum amount of contrast needed to detect the pattern; higher sensitivity corresponds to better performance. The data are stored in the data frame dat1. Each row contains the data from one subject; the four columns contain contrast sensitivity measured on four days.