1. In order to estimate the mean amount of time computer users spend on the inte

Question

1. In order to estimate the mean amount of time computer users spend on the internet each month, how many computer users must be surveyed in order to be 95% confident that your sample mean is within 11 minutes of the population mean? Assume that the standard deviation of the population of monthly time spent on the internet is 210 min. What is a major obstacle to getting a good estimate of the population mean? Use technology to find the estimated minimum required sample size.

2.A study of the ages of motorcyclists killed in crashes involves the random selection of 137 drivers with a mean of 38.01 years. Assuming that sigmaequals=11.4 years, construct and interpret a 90% confidence interval estimate of the mean age of all motorcyclists killed in crashes.

3.Salaries of 45 college graduates who took a statistics course in college have a mean, x overbarx, of $67,200. Assuming a standard deviation, of $17,637, construct a 95% confidence interval for estimating the population mean

Explanation / Answer

1. Here Margin of error=11

We need to find n for 95% CI so z value = 1.96

So using formula of Margin of error=z*sd/sqrt(n)

Hence n=(z*sd/E)^2=(1.96*210/11)^2=1400.12=1400

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