An ex of the vertical-horizontal illusion is shown in the figure. Although the two lines are exactly the same length, the vertical line appears to be much longer. To examine the strength of this illusion, a researcher prepared an ex in which both lines were exactly 10 inches long. The ex shown to individual participants who were told that the horizontal line was 10 inches long and then were asked to estimate the length of the vertical line. For a sample of n=25 participants, the average estimate was M=12.2 inches with a standard deviation of s=1.00.

a. Use a one-tailed hypothesis test with an alpha level of .01 to demonstrate that the individuals in the sample significantly overestimate the true length of the line. (Note: Accurate estimation would produce a mean of u=10 inches.)

b. find out the estimated r squared, the percentage of variance accounted for, to measure the size of this effect.