A study was conducted to estimate μ, the mean number of weekly hours that U.S. adults use computers at home. Suppose a random sample of 81 U.S. adults gives a mean weekly computer usage time of 8.5 hours and that from prior studies, the population standard deviation is assumed to be σ = 3.6 hours. The 95% confidence interval for the mean, μ, is (7.7, 9.3).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 sample of size 400 (instead of 81) Using a sample of size 36 (instead of 81) Using a different sample of size 81 Using a 90% level of confidence (instead of 95%) Using a 99% level of confidence (instead of 95%)

A study was conducted to estimate μ, the mean number of weekly hours that U.S. adults use computers at home. Suppose a random sample of 81 U.S. adults gives a mean weekly computer usage time of 8.5 hours and that from prior studies, the population standard deviation is assumed to be σ = 3.6 hours.We are 95% confident that the mean number of weekly hours that U.S. adults use computers at home falls between which of the following intervals?Group of answer choices7.7 and 9.37.3 and 9.76.5 and 10.58.4 and 8.68.1 and 8.9

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)

A study was conducted to estimate μ, the mean number of weekly hours that U.S. adults use computers at home. Suppose a random sample of 81 U.S. adults gives a mean weekly computer usage time of 8.5 hours and that from prior studies, the population standard deviation is assumed to be σ = 3.6 hours.A similar study conducted a year earlier estimated that μ, the mean number of weekly hours that U.S. adults use computers at home, was 8 hours. We would like to test (at the usual significance level of 5%) whether the current study provides significant evidence that this mean has changed since the previous year.Using a 95% confidence interval of (7.7, 9.3), which of the following is an appropriate conclusion? The current study does provide significant evidence that the mean number of weekly hours has changed over the past year, since 8 falls outside the confidence interval. The current study does not provide significant evidence that the mean number of weekly hours has changed over the past year, since 8 falls outside the confidence interval. The current study does provide significant evidence that the mean number of weekly hours has changed over the past year, since 8 falls inside the confidence interval. The current study does not provide significant evidence that the mean number of weekly hours has changed over the past year, since 8 falls inside the confidence interval. You cannot draw a conclusion because the only way to reach a conclusion is to find the p-value of the test.

A random sample of 160 households is selected to estimate the mean amount spent on electric service. A 95% confidence interval was determined from the sample results to be ($151, $216). Which of the following is the correct interpretation of this interval? There is a 95% chance that the mean amount spent on electric service is between $151 and $216. We are 95% confident that the mean amount spent on electric service among the 160 households is between $151 and $216. 95% of the households will have an electric bill between $151 and $216. We are 95% confident that the mean amount spent on electric service among all households is between $151 and $216

Suppose we are interested in studying a population to estimate its mean. The population is normal and has a standard deviation of =σ23. We have taken a random sample of size =n95 from the population. This is Sample 1 in the table below. (In the table, Sample 1 is written "S1", Sample 2 is written "S2", etc.) As shown in the table, the sample mean of Sample 1 is =x140.9. Also shown are the lower and upper limits of the 80% confidence interval for the population mean using this sample, as well as the lower and upper limits of the 95% confidence interval. Suppose that the true mean of the population is =μ140, which is shown on the displays for the confidence intervals.Press the "Generate Samples" button to simulate taking 19 more random samples of size =n95 from this same population. (The 80% and 95% confidence intervals for all of the samples are shown in the table and graphed.) Then complete parts (a) through (c) below the table.x 80%lowerlimit 80%upperlimit 95%lowerlimit 95%upperlimitS1 140.9 138.2 143.6 136.3 145.5S2 139.9 137.2 142.6 135.3 144.5S3 141.2 138.5 143.9 136.6 145.8S4 139.7 137.0 142.4 135.1 144.3S5 143.6 140.9 146.3 139.0 148.2S6 141.5 138.8 144.2 136.9 146.1S7 139.0 136.3 141.7 134.4 143.6S8 136.5 133.8 139.2 131.9 141.1S9 141.8 139.1 144.5 137.2 146.4S10 141.2 138.5 143.9 136.6 145.8S11 145.2 142.5 147.9 140.6 149.8S12 141.5 138.8 144.2 136.9 146.1S13 136.4 133.7 139.1 131.8 141.0S14 142.0 139.3 144.7 137.4 146.6S15 140.2 137.5 142.9 135.6 144.8S16 143.6 140.9 146.3 139.0 148.2S17 138.5 135.8 141.2 133.9 143.1S18 134.7 132.0 137.4 130.1 139.3S19 139.6 136.9 142.3 135.0 144.2S20 141.7 139.0 144.4 137.1 146.380% confidence intervals130.0150.095% confidence intervals130.0150.0(a)How many of the 80% confidence intervals constructed from the 20 samples contain the population mean, =μ140? (b)How many of the 95% confidence intervals constructed from the 20 samples contain the population mean, =μ140? (c)Choose ALL that are true. The center of the 80% confidence interval for Sample 1 is 140.9, because the center of a confidence interval for the population mean must be the sample mean. For each sample, the 80% confidence interval for the sample is included in the 95% confidence interval for the sample. Since Sample 19 and Sample 20 are drawn from the same population, the center of the 95% confidence interval for Sample 19 must be the same as the center of the 95% confidence interval for Sample 20. All of the 95% confidence intervals should be the same as each other. Since they are not all the same, there must have been errors due to rounding. None of the choices above are true.