Posted by Anonymous on .
A sample of 25 different payroll depts. found that the employees worked an average of 310.3 days a year with a standard deviation of 23.8 days. What is the 90% confidence interval for the average days worked by employees in all payroll departments?

statistics 
PsyDAG,
90% = mean ± 1.645 SEm
SEm = SD/√n