Exam 3: Displaying and Describing Categorical Data

Max wants to start a farm to grow mussels. He needs to determine the best environment for growing them. He is going to try two different amounts of salt in the water (salinity) and three different water temperatures. For his experiment he has 18 aquariums, each with 20 mussels. He wants to see which environment produces the largest mussels. -Would it make sense to have a control group that did not get any of the treatments described above?

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. -Identify the subjects.

Which of these is not an advantage of using a stratified sample instead of a simple random sample?

One manager suggesting just going to the stores in the city where the company is headquartered so they wouldn't have to travel far. What type of sampling would this be? Explain why this method is biased. Be sure to name the kind(s) of bias you describe and link it to the variable of interest.

Preservative Leather furniture used in public places can fade, crack, and deteriorate rapidly. An airport manager wants to see if a leather preservative spray can make the furniture look good longer. He buys eight new leather chairs and places them in the waiting area, four near the south-facing windows and the other four set back from the windows as shown. He assigned the chairs randomly to these spots. a. Use the random numbers given to decide which chairs to spray. Explain your method clearly. $32219 \quad 00597 \quad 86374$ b. Briefly explain why your assignment strategy is important in helping the manager assess the effectiveness of the leather preservative.

Suppose your local school district decides to randomly test high school students for attention deficit disorder (ADD). There are three high schools in the district, each with grades 9-12. The school Board pools all of the students together and randomly samples 250 students. Is this a simple random sample?

Placebos are a tool for

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.

A statistics teacher wants to know how her students feel about mathematics courses. She decides to administer a survey to a random sample of students taking a mathematics course. She has several sampling plans to choose from. Name the sampling strategy in each. a. There are four ranks of students taking the class: freshmen, sophomores, juniors, and seniors. Randomly select 15 students from each class rank. b. Randomly select ten math class sections and survey every student in each of those sections. c. Each student has a nine-digit student number. Randomly choose 60 different nine-digit numbers and survey the students that correspond to those numbers. d. Randomly select a number from 1 to 5. Using the class roster, start at that number, then select every fifth student from the list after that.

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. -State your conclusion.

A large manufacturer of batteries knows that, historically, 10% of its batteries come off the production line defective, and the remaining 90% of batteries come off the production line in working condition. Conduct a simulation to estimate how many batteries the company needs to pull off the production line in order to be sure of ending up with 10 working batteries. -Show three trials by clearly labeling the random number table given below. Specify the outcome of each trial. Trial 1: 10242 50692 18977 28370 82669 83236 77479 90618 43707 78695 Trial 2: 81183 48554 60809 39996 81915 25404 33366 92082 04822 79866 Trial 3: 06765 67041 20479 54612 13411 36837 69983 53082 43589 27865

Property taxes Administrators of the fire department are concerned about the possibility of implementing a new property tax to raise money needed to replace old equipment. They decide to check on public opinion by having a random sample of the city's population. a. Several plans for choosing the sample are proposed. Write the letter corresponding to the sampling strategy in the blank next to each plan. A. convenience; B. stratified; C. simple; D. cluster; E. systematic ___i. The city has five property classifications: single family homes, apartments, condominiums, temporary housing (hotel and campgrounds), and retail property. Randomly select ten residents from each category. ___ii. Each property owner has a 5-digit ID number. Use a random number table to choose forty numbers. ___iii. At the start of each week, survey every tenth person who arrives at the city park. ___ iv. Randomly select a housing classification (say, apartments) and survey all the people who live in that property classification. ___ v. Have each firefighter survey 10 of his/her neighbors. b. Name and briefly describe the kind of bias that might be present if the administration decides that instead of selecting people randomly they'll just… i. interview people about the new property tax at a fire station open house. ii. ask people who are willing to be taxed to sign a petition.

If the teacher in question 1 simply surveyed all of her students, what kind of sampling would that be? Explain why this method is biased. Be sure to name the kind(s) of bias you describe and link it to the variable of interest.

To check the effect of cold temperatures on the battery's ability to start a car, researchers purchased a battery from Sears and one from NAPA. They disabled a car so it would not start, put the car in a warm garage, and installed the Sears battery. They tried to start the car repeatedly, keeping track of the total time that elapsed before the battery could no longer turn the engine over. Then they Moved the car outdoors where the temperature was below zero. After the car had chilled there for several hours, the researchers installed the NAPA battery and repeated the test. Is this a good Experimental design?

Insulators Ceramics engineers are testing a new formulation for the material used to make insulators for power lines. They will try baking the insulators at four different temperatures, followed by either slow or rapid cooling. They want to try every combination of the baking and cooling options to see which produces insulators least likely to break during adverse weather conditions. a. What are the experimental units? b. How many factors are there? c. How many treatments are there? d. What is the response variable?

A chemistry professor who teaches a large lecture class surveys his students who attend his class about how he can make the class more interesting, hoping he can get more students to attend. This survey method suffers from

Listed below are the names of 20 students who are juniors. Use the random numbers listed below to select five of them to be in your sample. Clearly explain your method. Adam Chris Dave Deirdre Dick Ellen Eric Joan John Judi Joy Kenny Laura Mary Paul Peter Rachel Rob Sara Stacey $04028\quad55259\quad81183\quad40754\quad60209\quad06765\quad27306$ $28370\quad82669\quad83236\quad77479\quad90618\quad43707\quad78695$

An article in a local newspaper reported that dogs kept as pets tend to be overweight. Veterinarians say that diet and exercise will help these chubby dogs get in shape. The veterinarians propose two different diets (Diet A and Diet B) and two different exercise programs (Plan 1 and Plan 2). Diet A: owners control the portions of dog food and dog treats; Diet B: a mixture of fresh vegetables with the dog food and substitute regular dog treats with baby carrots. Plan 1: three 30-minute walks a week; Plan 2: 20-minute walks daily. Sixty dog owners volunteer to take part in an experiment to help their chubby dogs lose weight. -Identify the following: a. the subjects: b. the factor(s) and the number of level(s) for each: c. the number of treatments: d. whether or not the experiment is blind (or double-blind): e. the response variable:

The January 2005 Gallup Youth Survey telephoned a random sample of 1028 U.S. teens and asked these teens to name their favorite movie from 2004. Napoleon Dynamite had the highest percentage with 8% of teens ranking it as their favorite movie. Which is true? I. The population of interest is all U.S. teens II. 8% is a statistic and not the actual percentage of all U.S. teens who would rank this movie as their favorite. III. This sampling design should provide a reasonably accurate estimate of the actual percentage of all U.S. teens who would rank this movie as their favorite.

Gun control Two friends who strongly disagree on whether there should be stricter regulation of guns in this country want to conduct a poll of the students in their school to see which side most students agree with. Each came back with a different version of the question they want to ask. Version 1: Do you think the government should respect our 2nd Amendment rights and allow lawabiding citizens to own guns? Version 2: In the wake of recent mass shootings, should laws be passed to keep guns out of the hands of people with a history of violence? a. Which version would make it seem like people oppose stricter gun regulation? What kind of bias is this? b. Is the version you did not pick in part a less biased? c. Is it reasonable for a person to respond 'yes' to both questions?