Question

The average weekly income of teachers in one school district is $750 with a standard deviation of $85. Find the percentage of teachers earing more than $825 a week?

Answer 1

Point estimate (average) = $750
Standard deviation = $85
P(X>$825) = ?

Z = (X-mean)/Standard deviation = (825-750)/85 ≈ 0.88

From Z-table, P(X=825) = 0.8106

Therefore,
P(X>$825) = 1 - P(X=$825) = 1-0.8106 = 0.1894 = 18.94%

Percentage of teachers earning more than $825 is 18.94%.