Question

The distribution of results from a cholesterol test has a mean of 180 and a standard deviation of 20. A sample size of 40 is drawn randomly.

Find the probability that the sum of the 40 values is less than 6,950.

Answer 1

Solution :

Given that,

mean = = 180

standard deviation = = 20

n = 40

= 180

₌ / n = 20 40 = 3.1623

  = (x / n)

= 6950 / 40

= 173.75

P( < 173.75 )

P ( - /) < ( 173.75 - 180 / 3.1623)

P ( z < -6.25 / 3.1623 )

P ( z < - 1.98 )

= 0.0239

Probability = 0.0239