Question

In Utopia, the number of children per family is normally distributed and the mean is 8. IF 10% of families have 13 or more children, what is the standard deviation of the distribution?

Answer 1

You have to look on a standard normal table to find Z value that corresponds with 10% area to right of that value or 90% to left

P(Z>13) = .1 or P(Z<13) = .9
usually tables list probability to the left, so look up 90% or .9 in table and use that
z-value

then find std dev with equation

\[Z = \frac{X - mean}{std dev}\]

Answer 2

thank you!