Question

Among college students who hold part-time jobs during the school year, the distribution of the time spent working per week is approximately normally distributed with a mean of 20.20 hours and a standard deviation of 2.60 hours. Find the probability that the average time spent working per week of 18 randomly selected college students who hold part-time jobs during the school year is

Answer 1

0.2005

Explanation:

here,

mean = 20.20

standard deviation = 2.60

we know that,

Z score = (X-mean)/standard deviation

for X = 18:

Z score = (18-20.20)/2.6 = -0.8461

note that the z score is negative because the measured value is less than the mean value.

for Z score 0.8461 probability is 0.7995

and since the z score is negative the actual probability would be

1-0.7995 = 0.2005