I followed the example in the books but yet my prof says I am wrong.


Q1:Assume the speed of vehicles along a stretch of I-10 has an approximately normal distribution with a mean of 71 mph and a standard deviation of 8 mph.

a. The current speed limit is 65 mph. What is the proportion of vehicles less than or equal to the speed limit?

0.22660000000000002

b. What proportion of the vehicles would be going less than 50 mph?

0.0043

Seems that missed c and d but prof gave me credit for other partially correct answers.

Still pissed.

Do you use your calculator or tables from the books?  My prof had us round to 4 places, brutal if yours makes you go father, for no reason really.

... especially since the mean and SD are only given to one or two significant digits.

I would have failed you for using so many insignificant digits.