Explore BrainMass

Explore BrainMass

    Statistics - Confidence Interval

    This content was COPIED from BrainMass.com - View the original, and get the already-completed solution here!

    Please help with the following problems. Provide step by step calculations.

    1. The security department of a university is planning its budget for the next year. in estimating the man-hours for security during university sponsored music concerts, the average length of music concerts is needed. A random sample from 36 security depts. at universitites was taken and the sample mean length of concerts was 160 minutes. Suppose the population standard deviation is 45 minutes. A 95% confidence interval for the true mean duration of music concerts is?

    2. You are interested in determining the average cost of a 3 minute phone call to locations in the US. what sample size must you take to be 96% confident that the results will be within $.75 of the true mean cost per call? From the phone company you have gotten an estimate of o = 7.71

    © BrainMass Inc. brainmass.com June 3, 2020, 10:15 pm ad1c9bdddf

    Solution Preview

    (1) m = 160, n = 35, s = 45

    SE = s/sqrt n = 45/sqrt 36 = 7.5

    The 95% CI is given by [m - ...

    Solution Summary

    This solution helps with question about population standard deviation. Complete, Neat and Step-by-step Solutions are provided.