The mean of a normally distributed data set is 12, and the standard deviation is 2.

Question

___% of the data points lies between 8 and 16.

Find the percentage

Answer 1

8 is 2 std below the mean
16 is 4 std above the mean

P(Z>4) = .9772
P(Z>8) = .0227
P(4<Z<8) = .9772-.0228 = .9545

You can play around with this stuff at

http://davidmlane.com/hyperstat/z_table.html