posted by DezShonna K on .
The average age of statistics students nationwide is 22. The standard deviation is 2.5 years. Assume the age is a normally distributed variable.
Find the probability that one student selected at random is older than 23.
Find the probability that the mean age of a group of 16 students selected at random is bigger than 23
Z = (score - mean)/SD
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion above that Z score.
Z = (mean1 - mean2)/standard error (SE) of difference between means
SEdiff = √(SEmean1^2 + SEmean2^2)
SEm = SD/√(n-1)
Since only one SD is provided, you can use just that to determine SEdiff.
Use same table.