For each sample of 16 boxes of cereal an average box weight is recorded. Past records indicate that on the average 1 out of 40 of these average box weights exceeds 8.4 ounces and 1 out of 40 is less than 8.1 ounces. What is the prob that an individual box of cereal selected at random will weight less than 8 ounces?

Does my solution make sense?

Pr(x>8.4ozs) = 1/40=0.025

Pr(x<8.1ozs) = 1/40=0.025

z value associated with pr 0.025 is 1.96

therefore, Pr(x<8.0) for 1 of 16 boxes at random is df = 15, ...and now i am getting confused. Please help. Thanks.