13.60 [EX13-60] Diopters represent the amount of correction needed to provide 20/20, or normal, vision. The greater the degree of nearsighted or farsighted vision, the higher the corrective prescription in diopters. Measurements in negative diopters refer to nearsighted vision, whereas measurements in positive diopters refer to farsighted vision. A sample of 30 competitive contact lenses was taken from a lot shipped to a company for analyses. Acceptance of the lot depended on the relationship between the lens power, which is measured in diopters, and a certain optical effect labeled C/O. The sample data (coded in two manners)

follow.

Group 1 Power C/O

0.25 0.105

0.50 0.106

••• Remainder of data on Student’s Suite CD-ROM.

Courtesy of Bausch & Lomb

a. Draw a scatter diagram of these data. The xterm is lens power.

b. Calculate the correlation coefficient between the two variables.

c. Test for a significant correlation at the 0.05 level of significance.

d. Find the equation of the line of best fit.

e. Determine whether there is a linear relationship between C/O and lens power for Group 1 by testing the significance of the results (slope of the line of best fit) found in part

d. Use

  0.05.