The 9th percentile of the bill amounts is 81.0634.
<h3>How to calculate the percentile?</h3>
Population mean, µ = 110.56
Population standard deviation, σ = 22
a) p = 0.09
Z score at p = 0.09 using excel = NORM.S.INV(0.09) = -1.3408
Value of X = µ + z*σ = 110.56 + (-1.3408)*22 = 81.0634
9th percentile = 81.0634
b) p = 0.66
Z score at p = 0.66 using excel = NORM.S.INV(0.66) = 0.4125
Value of X = µ + z*σ = 110.56 + (0.4125)*22 = 119.6342
66th percentile = 119.6342
c) Median = 0.50
Z score at p = 0.5 using excel = NORM.S.INV(0.5) = 0
Value of X = µ + z*σ = 110.56 + (0)*22 = 110.56
Median = 110.56
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