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 standard error of the mean in this example?

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 greater than 320 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 $\alpha$ $= .05$

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?

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

Crossett Trucking Company claims that the mean weight of its delivery trucks when they are fully loaded is 6,000 pounds and the standard deviation is 150 pounds. Assume that the population follows the normal distribution. Forty trucks are randomly selected and weighed. Within what limits will 95 percent of the sample means occur?

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?

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

The rent for a one-bedroom apartment in Southern California follows the normal distribution with a mean of $2,200 per month and a standard deviation of$250 per month. The distribution of the monthly costs does not follow the normal distribution. In fact, it is positively skewed. What is the probability of selecting a sample of 50 one bedroom apartments and finding the mean to be at least $1,950 per month?

In the law firm Tybo and Associates, there are six partners. Listed is the number of cases each partner actually tried in court last month.

$$\begin{array}{|lc|} \hline \text { Partner } & \text { Number of Cases } \\ \hline \text { Ruud } & 3 \\ \text { Wu } & 6 \\ \text { Sass } & 3 \\ \text { Flores } & 3 \\ \text { Wilhelms } & 0 \\ \text { Schueller } & 1 \end{array}$$

a. How many different samples of size 3 are possible? b. List all possible samples of size 3 , and compute the mean number of cases in each sample. c. Compare the mean of the distribution of sample means to the population mean. d. On a chart similar to Chart $8-2$, compare the dispersion in the population with that of the sample means.

A normal population has a mean of 75 and a standard deviation of 5. You select a sample of 40. Compute the probability the sample mean is: a. Less than 74. b. Between 74 and 76. c. Between 76 and 77. d. Greater than 77

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 Georgetown, South Carolina, Traffic Division reported 40 percent of high-speed chases involving automobiles result in a minor or major accident. During a month in which 50 high-speed chases occur, what is the probability that 25 or more will result in a minor or major accident?