A pupillometer is a device used to observe changes in pupil dilations as the eye is exposed to different visual stimuli. Since there is a direct correlation between the amount an individual's pupil dilates and his or her interest in the stimuli, marketing organizations sometimes use pupillometers to help them evaluate potential con sumer interest in new products, alternative package designs, and other factors (Optical Engineering, Mar.

1995). The Design and Market Research Laboratories of the Container Corporation of America used a pupillometer to evaluate consumer reaction to different silvcrware patterns for a client. Suppose 15 consumers were chosen at random, and each was shown two silverware patterns. Their pupillometer readings (in millimeters) are shown in the table on page 373.

a. What are the appropriate null and alternative hypotheses to test whether the mean amount of pupil dilation differs for the two patterns? Define any symbols you use.

b. The data were analyzed using MINITAB, with the results shown in the printout (p. 373). Interpret these results.

c. Is the paired difference design used for this study preferable to an independent samples design? For independent samples we could select 30 consumers, divide them into two groups of 15, and show each group a differcnt pattern. Explain your preference.