Question

The mean of a normally distributed data set is 118, and the standard deviation is 16.

a) Use the standard normal table to find the probability that a randomly-selected data value is greater than 140.

b) Use the standard normal table to find the probability that a randomly-selected data value is less than 90.

Answer 1

Step-by-step explanation:

a)

z = (140 - 118)/16 = 22/16 = 11/8 = 1.375 ≈ 1.38

in the z-table this gives us the p-value : 0.91621

that is the probability of values 140 and below.

for above 140 we need to calculate the value of the other side of the bell-curve :

1 - 0.91621 = 0.08379

b)

z = (90 - 118)/16 = -28/16 = -7/4 = -1.75

in the z-table this gives us the p-value : 0.04006

that is the probability of values of 90 and below.