Question

For mean 25 and standard deviation 3, how much area is under the bell shaped curve within 2 standard deviations of the mean?

Answer 1

`0.6826`

Explanation:

`P(25-3 < X < 25+3) = P(22 < X < 28)`

`P(22 < X < 28) = P((22-25)/3 < z < (28-25)/3)`

#P(22 < X < 28) =P(-1 < z < 1)

from Normal Distribution Table,
`P(-1 < z < 1) = 0.6826`