Standard deviation question

Question

The mean weight of loads of rock is 43.0 tons with a standard deviation of 12.0 tons. If 16 loads are chosen at random for a weight check, we wish to compute the probability that the mean weight of those loads is less than 39.8 tons. Assume that the variable is normally distributed.
The standard deviation for the sampling distribution of means for this problem is

Select one:

a. 12.0

b. 4.0

c. 3.0

d. 1.0

e. 0.75

Answer 1

s= σ/√n = 12/√16 = 3