Exam 8: Regression, Associations, and Predictive Modeling

Over the trial month, 6% of the computer chips manufactured were defective. Management decided that this decrease was significant. Why might management choose not to permanently institute the employee incentive program?

Verify that this scenario satisfies all four conditions for a binomial scenario.

Show three trials by clearly labeling the random number table given below. Specify the outcome of each trial. Trial 1: 10242506921897728370826698323677479906184370778695 Trial 2: 81183485546080939996819152540433366920820482279866 Trial 3: 06765670412047954612134113683769983530824358927865

Which is not a critical part of designing a good experiment?

Test an appropriate hypothesis and state your conclusion. (Make sure to check any necessary conditions and to state a conclusion in the context of the problem.)

Sweet potato pie Sam is preparing sweet potato pies as his dessert for Thanksgiving. The store he shops at sells six sweet potatoes in a bag. He has found that each bag will contain 0, 1, or 2 bad sweet potatoes. Based on experience he estimates that there will be no bad sweet potatoes in 40% of the bags, one bad sweet potato in 30% of the bags, and two bad sweet potatoes in the rest. Conduct a simulation to estimate how many bags Sam will have to purchase to have three dozen sweet good potatoes. a) Describe how you will use a random number table to conduct this simulation. b) Show two trials by clearly labeling the random number table given below. Specify the outcome for each trial. c) State your conclusion.

All but one of these statements contain a mistake. Which could be true?

A random sample of 120 classrooms at a large university found that 70% of them had been cleaned Properly. What is the standard error of the sample proportion?

The company wants to estimate the true percentage of 16- to 24-year old cell phone owners who use their phone to go online to within $\pm 7.5 \% \text {, with } 95 \%$ fidence. How many cell phone owners in this age group should they sample?

Here is a scatterplot of weight versus height for students in an introductory statistics class. The men are coded as "1" and appear as circles in the scatterplot; the women are coded as "2" and appear as squares in the scatterplot. a. Do you think there is a clear pattern? Describe the association between weight and height. b. Comment on any differences you see between men and women in the plot. c. Do you think a linear model from the set of all data could accurately predict the weight of a student with height 70 inches? Explain.

Identify the response variable.

He had 280 customers that day. Assuming this day was typical for his store, what would be the mean and standard deviation of the number of customers who buy magazines each day?

A marketing company reviewing the length of television commercials monitored a random sample Of commercials over several days. They found that a 95% confidence interval for the mean length (in seconds) of commercials aired daily was (23, 27). Which is true?

Autos Hoping to improve the gas mileage of their cars, a car company has made an adjustment in the manufacturing process. Random samples of automobiles coming off the assembly line have been measured each week that the plant has been in operation. The data from before and after the manufacturing adjustments were made are in the table. It is believed that measurements of gas mileage are normally distributed. Write a complete conclusion about the manufacturing adjustments based on the statistical software printout shown below.

What is the probability that he does not sell a magazine until the 8th customer? Show work.

A friend of yours plans to toss a fair coin 200 times. You watch the first 20 tosses and are surprised That she got 15 heads. But then you get bored and leave. How many heads do you expect her to Have when she has finished all 200 tosses?

Suppose that a conveyor used to sort packages by size does not work properly. We test the conveyor on several packages (with $H _ { 0 }$ : incorrect sort) and our data results in a $P$ -value of $0.016$ . What probably happens as a result of our testing?

Name and describe the kind of bias that might be present if the administration decides that instead of subjecting people to random testing they'll just… a. interview employees about possible drug abuse. b. ask people to volunteer to be tested.

Packing Line A packing company investigates hiring a national training consultant to improve productivity on their packing line. The consultant is very expensive, so they will only hire him if they are very sure that productivity will rise. The company hires the consultant for a one-week trial to work with 18 employees before making a final decision about the training program. The training program will be implemented if the average units packed per employee increases by more than 10 cases per day. The company manager will test a hypothesis using α = 0.05. a. Write appropriate hypotheses (in words and in symbols). b. In this context, which do you consider to be more serious - a Type I or a Type II error? Explain briefly. c. After this trial produced inconclusive results the manager decided to test the training program again with another group of employees. Describe two changes he could make in the trial to increase the power of the test, and explain the disadvantages of each.

Write a sentence or two about the conditional relative frequency distribution of the breeds among female respondents.