statistics
posted by Joey .
A manager states that in his factory, the mean number of days per year missed by his employees is less than the national mean of 10. The following data is days missed by some of his employees last year (mean=5.025, standard deviation=3.634). Is there sufficient avidence to belive the manager's statement?

Which "some of his employees"? How many employees were in his sample?
The standard error of the mean (SEm) for a distribution of means is like the standard deviation (SD) for a distribution of scores.
SEm = SD/√n, where n = number of subjects in his sample.
Does this help you answer the question?