A human resource manager for a large company takes a random sample of 60 employees from the company database. Based on the sample she calculates a 95% confidence interval for the mean time of employment for all employees to be 8.7 to 15.2 years.

Which of the following will provide a more informative (i.e., narrower) confidence interval than the 95% confidence interval? Check all that apply.

Using a 90% confidence level (instead of 95%)Using a 99% confidence level (instead of 95%)Using a sample size of 40 employees (instead of 60)Using a sample size of 90 employees (instead of 60)- unanswered