Exam 3: Displaying and Describing Categorical Data

Suppose the state decides to randomly test high school wrestlers for steroid use. There are 16 teams in the league, and each team has 20 wrestlers. State investigators plan to test 32 of these athletes by randomly choosing two wrestlers from each team. Is this a simple random sample?

On January 1 of every year, many people watch the Rose Parade on television. The week before the parade is very busy for float builders and decorators. Roses, carnations, and other flowers are purchased from around the world to decorate the floats. Based on past experience, one float decorator found that 10% of the bundles of roses delivered will not open in time for the parade, 20% of the bundles of roses delivered will have bugs on them and be unusable, 60% of the bundles of roses will turn out to be beautiful, and the rest of the bundles of roses delivered will bloom too early and start to discolor before January 1. Conduct a simulation to estimate how many roses the float decorator will need to purchase to have 15 good bundles of roses to place on the float. -State your conclusion.

A company sponsoring a new Internet search engine wants to collect data on the ease of using it. Which is the best way to collect the data?

Researchers plan to investigate a new medication that may reduce blood pressure for individuals with higher than average blood pressure. 90 volunteers with higher than average blood pressure are solicited. Volunteers are randomly assign 100 mg of the medicine, 200 mg of the medicine, or a placebo. Blood pressure will be measured at the beginning and at the conclusion of the study. -Describe an advantage to random assignment of treatment.

Design an experiment to determine if the home teams have an unfair advantage when shooting free-throws.

Good CDs Brian is a systems manager for a large company. In his work, he has found that about 5% of all CDs he orders are bad. He needs to give one of the executives at his company five good CDs. Conduct a simulation to estimate how many CDs Brian will have to check to get five good CDs for the executive. a. Describe how you will use a random number table to conduct this simulation. b. Show three trials by clearly labeling the random number table given below. Specify the outcome for each trial. Trial Simulation Outcome \#1 03242506921897728370 \#2 78695214028552581183 \#3 60809067653999681915 c. State your conclusion.

The owner of a car dealership planned to develop strategies to increase sales. He hoped to learn the reasons why many people who visit his car lot do not eventually buy a car from him. For one Month he asked his sales staff to keep a list of the names and addresses of everyone who came in to test drive a car. At the end of the month he sent surveys to the people who did not buy the car, asking them why. About one third of them returned the survey, with 44% of those indicating that they found a lower price elsewhere. Which is true? I. The population of interest is all potential car buyers. II. This survey design suffered from non-response bias. III. Because it comes from a sample 44% is a parameter, not a statistic.

A school district administrator sent a survey to all teachers in the district. Only 30% of the teachers responded to the survey. Which of the following is true? I. The people that did not responded are likely to be similar to those that did so he should use them as the sample. II. This survey design suffered from non-response bias. III. Because he sent the survey to everyone, this is a census and the results can be applied to the Whole population.

Candy packaging Marketing researchers wonder if the color and type of a candy's packaging may influence sales of the candy. They manufacture test packages for chocolate mints in three colors (white, green, and silver) and three types (box, bag, and roll). Suspecting that sales may depend on a combination of package color and type, the researchers prepare nine different packages, then market them for several weeks in convenience stores in various locations. In this experiment, a. what are the experimental units? b. how many factors are there? c. how many treatments are there? d. what is the response variable?

As a 4-H project, Billy is raising chickens. He feeds and waters them every day, and collects the eggs every other day, selling them to people in the neighborhood. He has found that each hen's nest will contain from 0 to 2 eggs. Based on past experience he estimates that there will be no eggs in 10% of the nests, one egg in 30% of the nests, and 2 eggs in the other 60%. Conduct a simulation to estimate how many nests Bill will have to visit to collect a dozen eggs. -Show three trials by clearly labeling the random number table given below. Specify the outcome for each trial. 57528 78305 63508 29418 90676 31993 54636 17877 31574 28042 72621 84818

Moods A headline in the New York Times announced "Research shows running can alter one's moods." The article reported that researchers gave a Personality Assessment Test to 231 males who run at least 20 miles a week, and found "statistically significant personality differences between the runners and the male population as a whole." Do you think the headline was appropriate? Explain.

Which is true about randomized experiments? I. Randomization reduces the effects of confounding variables. II. Random assignment of treatments allows results to be generalized to the larger population. III. Blocking can be used to reduce the within-treatment variability.

Announcements. A high school in Wisconsin stopped having announcements read to students over the intercom system, choosing to have announcements displayed on television monitors located throughout the building. To see how students feel about the new system the principal wants to conduct a survey. Explain how to select a sample of about 500 students using each sampling method below: a. Simple random sample b. Stratified random sample with grade levels as strata c. Cluster sample with classrooms as clusters

A company has tried to improve the effectiveness of its dishwashing detergent and wants to see if it works better than the original formula. They use 6 identical new dishwashers and load them identically with dirty dishes. Three packs of each of the two types of detergent are used, and they are randomly assigned to one of the six dishwashers. After the load is run, they rate each load for overall cleanliness. Which of the following is true?

Which statement about bias is true? I. Bias results from random variation and will always be present. II. Bias results from a sampling method likely to produce samples that do not represent the population. III. Bias is usually reduced when sample size is larger.

Management at a retail store is concerned about the possibility of drug abuse by people who work there. They decide to check on the extent of the problem by having a random sample of the employees undergo a drug test. Several plans for choosing the sample are proposed. Name the sampling strategy in each. a. Randomly select ten stores around the country and survey all the employees that work at those stores. b. Choose the fourth person that arrives to work for each shift. c. There are four employee classifications: supervisors, fulltime clerks, part-time clerks, and maintenance staff. Randomly select ten people from each category. d. Each employee has a three-digit identification number. Randomly choose 40 numbers.

As a 4-H project, Billy is raising chickens. He feeds and waters them every day, and collects the eggs every other day, selling them to people in the neighborhood. He has found that each hen's nest will contain from 0 to 2 eggs. Based on past experience he estimates that there will be no eggs in 10% of the nests, one egg in 30% of the nests, and 2 eggs in the other 60%. Conduct a simulation to estimate how many nests Bill will have to visit to collect a dozen eggs. -Describe how you will use a random number table to conduct this simulation.

Military funding A college group is investigating student opinions about funding of the military. They phone a random sample of students at the college, asking each person one of these questions (randomly chosen): A: "Do you think that funding of the military should be increased so that the United States can better protect its citizens?" B: "Do you think that funding of the military should be increased?" Which question do you expect will elicit greater support for increased military funding? Explain. What kind of bias is this?

Listed at the right are the names of twenty full-time clerks on the retail staff. Use the random numbers listed below to select four of them to be in your sample. Clearly explain your method. 18192 95318 02975 01191 29958 09275 89141 61909 Larry Marissa Tim Diane Carol Joshua Barbara Allan Rich Sharyn Brian Kelly Nicole John June Frank Steve Andrea Matthew Erin

For a school project, Max must design a survey. For his survey he plans to randomly select families and gather information about all the children in each of those families. He must have at least 20 children in his sample. The number of children per family in the U.S. is given in the table below. How many families should Max expect to survey to reach at least 20 children? (treat “5 or more” as 5.) No. of Children 0 1 2 3 4 5 or more \% of families 17 23 25 16 10 9 -Show three trials by clearly labeling the random number table given below. Specify the outcome for each trial. 84432 04916 52949 78533 62350 20584 56367 19701 58765 41760 43304 13399 97198 40974 45301 60177 35604 21580