An IRS research found that the average time for taxpayers to prepare, copy, and electronically file a 1040 tax form is 330 minutes. The standard deviation for this time distribution, which is normal, is 80 minutes. A group of 40 taxpayers are chosen at random by a consumer protection organisation. What is the likelihood the sample mean is between 320 and 350 minutes?

According to the IRS, taxpayers calling the IRS in $2017$ waited $13$ minutes on average for an IRS telephone assister to answer. Do callers who use the IRS help line early in the day have a shorter wait? Suppose a sample of $50$ callers who placed their calls to the IRS in the first $30$ minutes that the line is open during the day have a mean waiting time of $11$ minutes before an IRS telephone assister answers. Based on data from past years, you decide that it is reasonable to assume that the standard deviation of waiting times is $8$ minutes. Using these sample results, can you conclude that the waiting time for calls placed during the first $30$ minutes the IRS help line is open each day is significantly less that the overall mean waiting time of $13$ minutes? Use $\alpha$ $= .05$

According to an IRS study, it takes a mean of 330 minutes for taxpayers to prepare, copy, and electronically file a 1040 tax form. This distribution of times follows the normal distribution and the standard deviation is 80 minutes. A consumer watchdog agency selects a random sample of 40 taxpayers. a. What is the standard error of the mean in this example? b. What is the likelihood the sample mean is greater than 320 minutes? c. What is the likelihood the sample mean is between 320 and 350 minutes? d. What is the likelihood the sample mean is greater than 350 minutes?

At Western University the historical mean of scholarship examination scores for freshman applications is 900. Ahistorical population standard deviation $\sigma$= 180 is assumed known. Each year, the assistant dean uses a sample of applications to determine whether the mean examination score for the new freshman applications has changed.

Use the confidence interval to conduct a hypothesis test. Using $\alpha$= .05, what is your conclusion?

At Western University the historical mean of scholarship examination scores for freshman applications is 900. Ahistorical population standard deviation $\sigma$= 180 is assumed known. Each year, the assistant dean uses a sample of applications to determine whether the mean examination score for the new freshman applications has changed.

What is the p-value?

A population consists of the following five values: 2, 2, 4, 4, and 8. a. List all samples of size 2, and compute the mean of each sample. b. Compute the mean of the distribution of sample means and the population mean. Compare the two values. c. Compare the dispersion in the population with that of the sample means

A population consists of these values: 2, 3, 6, 8, 11, 18.

At Western University the historical mean of scholarship examination scores for freshman applications is 900. Ahistorical population standard deviation $\sigma$= 180 is assumed known. Each year, the assistant dean uses a sample of applications to determine whether the mean examination score for the new freshman applications has changed.

State the hypotheses.

A normal population has a mean of 75 and a standard deviation of 5. You choose a 40-person sample. Calculate the likelihood that the sample mean is less than 74.

At the downtown office of First National Bank, there are five tellers. Last week, the tellers made the following number of errors each: 2, 3, 5, 3, and 5. a. How many different samples of 2 tellers are possible? b. List all possible samples of size 2 and compute the mean of each. c. Compute the mean of the sample means and compare it to the population mean

The average length of Majesty Video Production Inc.'s commercials should be 30 seconds. Assume that there is a normal distribution for ad length, with a population standard deviation of 2 seconds. Consider looking at a selection of 16 Majesty advertisements. What percent of the sample means will be greater than 28.25 seconds?

The average length of Majesty Video Production Inc.'s commercials should be 30 seconds. Assume that there is a normal distribution for ad length, with a population standard deviation of 2 seconds. Consider looking at a selection of 16 Majesty advertisements. What can we say about the shape of the distribution of the sample mean time?

The average length of Majesty Video Production Inc.'s commercials should be 30 seconds. Assume that there is a normal distribution for ad length, with a population standard deviation of 2 seconds. Consider looking at a selection of 16 Majesty advertisements. What is the standard error of the mean time?

A recent study by the Greater Los Angeles Taxi Drivers Association showed that the mean fare charged for service from Hermosa Beach to Los Angeles International Airport is $21 and the standard deviation is$3.50. We select a sample of 15 fares. a. What is the likelihood that the sample mean is between $20 and$23? b. What must you assume to make the above calculation?