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Answer:
0.8224
Step-by-step explanation:
Data
- mean: $76
- standard deviation, sd: $10
- first value of interest, x1: $63
- second value of interest, x2: $90
z-score for x1:
z1 = (x1 - mean)/sd = (63 - 76)/10 = -1.3
z-score for x2:
z2 = (x2 - mean)/sd = (90 - 76)/10 = 1.4
The proportion of wrist watch prices are between $63 and $90 is:
P(z1 < z < z2) = P(z < 1.4) - P(z < -1.3)
P(z < 1.4) = 0.9192 (see first picture attached)
P(z < -1.3) = 0.0968 (see second picture attached)
P(z1 < z < z2) = 0.9192 - 0.0968 = 0.8224
