Reduced visual performance with increasing age has been a much-studied phenomenon in recent years. This decline is due partly to changes in optical properties of the eye itself and partly to neural degeneration throughout the visual system. As one aspect of this problem, the article “Morphometry of Nerve Fiber Bundle Pores in the Optic Nerve Head of the Human”

(Experimental Eye Research [1988]: 559– 568) presented the accompanying data on x 5 age and y 5 percentage of the cribriform area of the lamina scleralis occupied by pores.

x 22 25 27 39 42 43 44 46 46 y 75 62 50 49 54 49 59 47 54 x 48 50 57 58 63 63 74 74 y 52 58 49 52 49 31 42 41

a. Suppose that prior to this study the researchers had believed that the average decrease in percentage area associated with a 1-year age increase was .5%. Do the data contradict this prior belief? State and test the appropriate hypotheses using a .10 significance level.

b. Estimate true average percentage area covered by pores for all 50-year-olds in the population in a way that conveys information about the precision of estimation.