Question 752357
Q: suppose the average age of a passenger train car is 19.3 years.  If the distribution of ages is normal and 10% of the cars are older than 22.2 years, find the standard deviation. please round your final answer to two decimal places.
------------------------------------------------------------------------
A:
P(X > 22.2) = 0.10
{{{P(Z > (22.2 - 19.3)/sigma)}}} = 0.10
{{{(22.2 - 19.3)/sigma}}} = {{{z[0.10]}}} = 1.282
{{{sigma}}} = {{{(22.2 - 19.3)/1.282}}}
standard deviation, {{{sigma}}} = {{{highlight(2.26)}}}