Unit Test — Unit test Answers

A café wants to study how customers tip differently based on what they order. The distribution of tips given by customers who buy only a cup of coffee is bimodal with a mean of $0.29 and a standard deviation of $0.116. The distribution of tips given by customers who buy only a salad is approximately Normally distributed with a mean of $2.89 and a standard deviation of $1.18. If a random sample of 35 tips from customers who buy only a cup of coffee is selected and a random sample of 20 customers who buy only a salad is selected, what is the probability of a sample mean being at least $2.50 more for customers who buy only a salad than for those who buy only a cup of coffee?

The distribution of the number of items washed in a standard load of laundry is skewed left with a mean of 41 items and a standard deviation of 7.7 items. What is the probability that 50 randomly selected loads of laundry have a mean of more than 39.5 items?

The ages of the 5 officers for a school club are 18, 18, 17, 16, and 15. The minimum of the ages of the officers is 15. The table displays all possible samples of size 2 and the corresponding minimum for each sample.Using the minimums in the table, is the sample minimum an unbiased estimator?

A catering company provides packages for weddings and for showers. The cost per person for small groups is approximately Normally distributed for both weddings and showers. The mean cost for weddings is $82.30 with a standard deviation of $18.20, while the mean cost for showers is $65 with a standard deviation of $17.73. If 9 weddings and 6 showers are randomly selected, what is the probability the mean cost of the weddings is more than the mean cost of the showers?

The manager of a large grocery store wants to inspect an incoming shipment of oranges to determine the proportion of blemishes. One inspector, Mary, takes a random sample of 25 oranges, and another inspector, Pat, takes a random sample of 50 oranges. Which of the following statements about variability of the sample proportion is correct?

The time needed to broil cauliflower is approximately Normally distributed with a mean of 6 minutes and a standard deviation of 1.9 minutes. If a random sample of 100 batches of cauliflower is selected, what is the probability the mean broiling time is more than 6.5 minutes?

Hal and Jose are avid crossword puzzle solvers. Hal solves 48% of his crossword puzzles in under 30 minutes, while Jose solves 39% of his crossword puzzles in under 30 minutes. Suppose that Hal solves 22 crossword puzzles and Jose solves 26 crossword puzzles. Because nJpJ, nJ (1–pJ), and nH (1-pH) are all greater than 10, the Normal condition is met. Let H = the proportion of Hal’s crossword puzzles solved in under 30 minutes and J = the proportion of Jose’s crossword puzzles solved in under 30 minutes. What is the probability that Jose’s proportion of crossword puzzles solved in under 30 minutes is greater than Hal’s?Find the z-table here.

A cell phone provider has 85% of its customers rank their service as "satisfactory.” Nico takes a random sample of 75 customers from this cell phone provider. What is the probability that 83% or more of this sample ranks the provider’s service as "satisfactory”?Find the z-table here.

A bottled water company bottles varying sizes of water, from 8-ounce to 1-gallon containers. The company has determined that the mean quantity in their 20-ounce bottles is 20.8 ounces with a standard deviation of 0.6 ounces. The bottling plant manager believes his machines are overfilling the bottles. A random sample of 30 bottles is taken, and the mean number of ounces of water is recorded. Which of the following values of the mean of the sample is most likely to occur if the true mean number of ounces is 20.8?

In a large high school, 37% of the teachers believe that five minutes is not enough time for students to change classes. However, 89% of the students believe that five minutes is not enough time for students to change classes. Let and be the sample proportions of teachers and students, respectively, who believe that five minutes is not enough time for students to change classes. Suppose 28 teachers and 100 students are selected at random and asked their opinion on the amount of time students have to change class.Which of the following is the correct shape and justification of the sampling distribution of ?

In a large high school, 37% of the teachers believe that five minutes is not enough time for students to change classes. However, 89% of the students believe that five minutes is not enough time for students to change classes. Let and be the sample proportions of teachers and students, respectively, who believe that five minutes is not enough time for students to change classes. Suppose 28 teachers and 100 students are selected at random and asked their opinion on the amount of time students have to change class.Which of the following is the mean of the sampling distribution of ?

A bottled water company bottles varying sizes of water, from 8-ounce to 1-gallon containers. The company has determined that the mean quantity in their 20-ounce bottles is 20.8 ounces with a standard deviation of 0.6 ounces. The bottling plant manager believes his machines are overfilling the bottles. A random sample of 30 bottles is taken, and the mean number of ounces of water is determined to be 21. Under the assumption that the true mean ounces of water is 20.8, 100 simulated means for samples of size 30 are shown in the dotplotWhat does the dot above 21 represent?

An air-conditioning repair technician claims to complete 67% of repairs in under an hour. A random sample of 31 repairs was chosen, and 22 of those were completed in under an hour. Let = the proportion of the random sample that were completed in under an hour.The probability that 71% or more of this technician’s repairs were completed in under an hour is 0.317. Does this result provide convincing evidence against the technician’s claim?

A conference consists of 5 sessions: A, B, C, D, and E. Here are the costs of the sessions.Session A: $50Session B: $50Session C: $100Session D: $150Session E: $200Here is a graph of the cost of all 5 sessions.A participant plans to attend 3 sessions. Here is a list of all possible samples of size 3 sessions from this population of 5 sessions: ABC, ABD, ABE, ACD, ACE, ADE, BCD, BCE, BDE, and CDE.Here is a graph displaying the minimum session cost for each possible sample of 3 sessions.The participant chooses 3 sessions at random from the list of all 5 sessions. The result of the random selection is sessions B, D, and E.Here is a graph displaying the distribution of session cost for this sample.

A real estate agent has 4 homes for sale: A, B, C, and D. Here are the listing prices.Home A: $150,000Home B: $250,000Home C: $190,000Home D: $550,000The agent wants to randomly select 2 of the 4 homes to show in an open house this coming weekend. This means the agent may show home A and B, A and C, A and D, B and C, B and D, or C and D. Which of the following gives the sampling distribution of the sample mean listing price for all possible samples of size 2 from this population of 4 homes?