Question

A recent survey found that 7575​% of all adults over 50 wear glasses for driving. In a random sample of 4040 adults over​ 50, what is the mean and standard deviation of those that wear​ glasses? Round the answers to the nearest hundredth.

Answer 1

Mean = 30

standard Deviation = 2.74

Explanation:

Formula

mean = np

Standard Deviation =
`√(npq)`

from the question = 40

P = 75% or 0.75

q = 1 - p = 1 - 75% or 1 - 0.75

To find mean

mean = 40 x 0.75

= 30

For Standard Deviation (SD)

Standard Deviation =
`√(npq)`

=
`\sqrt{40 X 0.75 X 0.25`

=
`√(7.5)`

:. Standard Deviation = 2.74