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ID: 3129306 • Letter: A

Question

a.)

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b.)

A survey classified a large number of adults according to whether they were judged to need eyeglasses to correct their reading vision and whether they used eyeglasses when reading. The proportions falling into the four categories are shown in the table. (Note that a small proportion, 0.01, of adults used eyeglasses when in fact they were judged not to need them.) Used Eyeglasses for Reading Judged to Need Eyeglasses Yes No Yes No 0.42 0.11 0.01 0.46 If a single adult is selected from this large group, find the probability of each event. (Enter your answers to two decimal (a) The adult is judged to need eyeglasses (b) The adult needs eyeglasses for reading but does not use them. (c) The adult uses eyeglasses for reading whether he or she needs them or not.

Explanation / Answer

(A)

(a) P(judged to need eyeglasses) = 0.42+0.11 =0.53

(b) P(needs eyeglass but doesn't use them) = 0.11

(c) P( uses eyeglass irrespective of need)= 0.42+0.01 = 0.43

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(B)