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Exam 3: Gathering Data

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Question 51

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Video games A headline in a local newspaper announced "Video game playing can lead to better spatial reasoning abilities." The article reported that a study found "statistically significant differences" between teens who play video games and teens who do not, with teens who play video games testing better in spatial reasoning. Do you think the headline was appropriate? Explain.

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No, this was not a controlled experiment...

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Question 52

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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.

A) I and II only
B) I only
C) I, II, and III
D) II only
E) II and III only

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Question 53

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A statistics teacher wants to know how students in her school 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. 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. -If the teacher in 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.

Bone Builder Researchers believe that a new drug called Bone Builder will help bones heal after children have broken or fractured a bone. The researchers believe that Bone Builder will work differently on bone breaks than on bone fractures, because of differences in initial bone condition. Bone Builder will be used in conjunction with traditional casts. To test the impact of Bone Builder on bone healing, the researchers recruit 18 children with bone breaks and 30 children with bone fractures. Design an appropriate experiment to determine if Bone Builder will help bones heal.

In an experiment the primary purpose of blocking is to

Which of the following is not required in an experimental design?

Management at a large retail chain 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. 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. -Name and describe the kind of bias that might be present if the management decides that instead of subjecting people to random testing they'll just… a. Hold department meetings and drug test the employees that attend. b. Offer additional employee discounts for those employees who agree to be drug tested.

Administrators at a large hospital are 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. a. There are four employee classifications: doctors, medical staff (nurses, technicians, etc.) office staff, and support staff (custodians, maintenance, etc.). Randomly select ten people from each category. b. Each employee has a 4-digit ID number. Randomly choose 40 numbers. c. At the start of each shift, choose every tenth person who arrives for work. d. Randomly select five departments and test all the people who work in those department - doctors, nurses, technicians, clerks, custodians, etc. -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 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. -State your conclusion.

Does regular exercise decrease the risk of cancer? A researcher finds 200 women over 50 who Exercise regularly, pairs each with a woman who has a similar medical history but does not Exercise, then follows subjects for 10 years to see which group develops more cancer. This is a

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?

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 assigned 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 a disadvantage of using volunteers in this study.

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 Billy 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. $\begin{array} { l l l l } 57528 & 78305 & 63508 & 29418 \\90676 & 31993 & 54636 & 17877 \\31574 & 28042 & 72621 & 84818\end{array}$

Aggressiveness A recent study evaluated elementary age children for aggressiveness. This study found that the children who played video games were more likely to engage in aggressive or violent play at school. The researchers said the difference was statistically significant. a. Briefly explain what "statistically significant" means in this context. b. The news media reported that this study proved that playing computer games causes children to be aggressive or violent. Briefly explain why this conclusion is not justified. c. But perhaps it is true. We wonder if playing computer games can lead to aggressive or violent behavior in elementary school children. We find 50 young children whose families volunteer to participate in our research. Design an appropriate experiment. (You need not explain how to randomize.)

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?

Management at a large retail chain 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. 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. -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.

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 Billy will have to visit to collect a dozen eggs. -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.

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?

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.) $\begin{array} { | l | l | l | l | l | l | l | } \hline \text { No. of Children } & 0 & 1 & 2 & 3 & 4 & 5 \text { or more } \\\hline \text { \% of families } & 17 & 23 & 25 & 16 & 10 & 9 \\\hline\end{array}$ -Show three trials by clearly labeling the random number table given below. Specify the outcome for each trial. $84432\quad 04916\quad 52949\quad 78533\quad 62350\quad 20584$ $56367 \quad 19701 \quad 58765 \quad 41760 \quad 43304\quad 13399$ $97198 \quad 40974 \quad 45301 \quad 60177 \quad 35604 \quad 21580$