Commuters were asked how many times a week they stop for coffee on their way to work. A survey found a mean of 3 times a week with a standard deviation of 0.55. Find the probability that the sum of 100 values is more than 290.

Answer 1

I think the same as the probability that one is more than 2.90

mean = 3
we are at .1 below mean
Z = -.1/.55 = -.18
from normal table if Z = -.18 then F(z) about .421
so about 42% are below so about 58 % are above 2.9
For accurate table use
http://davidmlane.com/hyperstat/z_table.html

Answer 2

57.21% or .5721