Question

Assume that blood pressure readings are normally distributed with a mean of 117and a standard deviation of 6.4.If 64people are randomly​ selected, find the probability that their mean blood pressure will be less than 119.Round to four decimal places.

Answer 1

0.9938

Explanation:

We can find this probability using a test statistic.

The test statistic to use is the z-scores

Mathematically;

z-score = (x-mean)/SD/√n

from the question, x = 119 , mean = 117 , SD = 6.4 and n = 64

Plugging these values in the z-score equation above, we have;

z-score = (119-117)/6.4/√64

z-score = 2/6.4/8

z-score = 2.5

The probability we want to find is;

P(z < 2.5)

we can get this value from the standard normal distribution table

Thus; P(z < 2.5) = 0.99379

Which to four decimal places = 0.9938