Question

Suppose Abby tracks her travel time to work for 60 days and determines that her mean travel time, in minutes, is 35.6. Assume the travel times are normally distributed with a standard deviation of 10.3 min. Determine the travel time ? such that 26.11% of the 60 days have a travel time that is at least ?.

Answer 1

42.192 is the answer, make sure you round it to whatever amount of decimals.

if future googlers want to know how to do it, first find .2611 on the table which is -.64 and take the complement which is .64. You could also do 1-.2611 and find .7389 on the table, you still end up with .64. Set that equal to the standardization equation so (x-35.6)/10.3 = .64 and solve with algebra. Multiply 10.3 to both sides, add 35.6 and you get x.