A grain mill manufactures 100-pound bags of flour for sale in restaurant supply warehouses. Historically, the weights of bags of flour manufactured at the mill were normally distributed with a mean of 100 pounds and a standard deviation of 15 pounds.

Question

A grain mill  manufactures 100-pound bags of flour for sale in restaurant supply warehouses. Historically, the weights of bags of flour manufactured at the mill were normally distributed with a mean of 100 pounds and a standard deviation of 15 pounds.
a. What is the probability that the weight of a randomly selected bag of flour falls between 94 and 106 pounds?
b. if samples of 36 bags are taken, what is the standard error of the mean?
c.what is the probability that a sample of 36 bags of flour has a mean weight between 94 and 106?

PsyDAG · Answer

a. Z = (score-mean)/SD

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability related to the Z scores.

b. SEm = SD/√n

c. Z = (score-mean)/SEm

Use same table.