Exam 3: Displaying and Describing Categorical Data

Hoping to get information that would allow them to negotiate new rates with their advertisers, Natural Health magazine phoned a random sample of 600 subscribers. 64% of those polled said they use nutritional supplements. Which is true? I. The population of interest is the people who read this magazine. II. "64%" is not a statistic; it's the parameter of interest. III. This sampling design should provide the company with a reasonably accurate estimate of the Percentage of all subscribers who use supplements.

In an experiment the primary purpose of blocking is to reduce

A researcher wants to compare the performance of three types of pain relievers in volunteers suffering from arthritis. Because people of different ages may suffer arthritis of varying degrees of severity, the subjects are split into two groups: under 60 and over 60. Subjects in each group are randomly assigned to take one of the medications. Twenty minutes later they rate their levels of pain. This experiment…

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. -Identify the factors and levels.

A researcher identified 100 men over forty who were not exercising and another 100 men over forty with similar medical histories who were exercising regularly. She followed the men for several years to see if there was any difference between the groups in the rate of heart attacks. This is a(n) …

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.

UFOs. A National Geographic survey in 2012 found that 36% of Americans believe in aliens. (The outer-space kind, not visitors from foreign countries!) If you were to randomly select 10 Americans, what is the average number of believers you'd expect in your sample? Conduct a simulation to find out! a. Explain how you will use the random numbers listed below to conduct your simulation. b. Carefully label your simulation for 2 trials. Trial \# The run Outcome 1 98642 20639 23185 56282 69929 2 14125 38872 94168 71622 35940 c. State your conclusion.

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 -Describe how you will use a random number table to conduct this simulation.

More dogs are being diagnosed with thyroid problems than have been diagnosed in the past. A researcher identified 50 puppies without thyroid problems and kept records of their diets for several years to see if any developed thyroid problems. This is a(n)

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. -Is this study blind?

Does donating blood lower cholesterol levels? 50 volunteers have a cholesterol test, then donate blood, and then have another cholesterol test. Which aspect of experimental design is present?

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 the subjects for 10 years to see which group develops more cancer. This is a

One administrator suggested walking into the break room and testing the people in there. 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.

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. -Someone suggested that Max arrange the tanks so that six with the lowest temperature are on one end of the room, and the six with the highest temperature are at the other end of the room. Explain how this could introduce confounding into the experiment.

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.

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 -State your conclusion.

Double-blinding in experiments is important so that I. The evaluators do not know which treatment group the participants are in. II. The participants do not know which treatment group they are in. III. No one knows which treatment any of the participants are getting.

It was discovered that a larger proportion of children who slept with nightlights later developed nearsightedness, compared to children who did not sleep with nightlights. The headlines read, "Leaving a light on for you children causes nearsightedness!" Later it was pointed out that nearsighted people have more trouble seeing in the dark and are more likely to leave lights on at night for their kids. And those same nearsighted parents are likely to have nearsighted kids. This is an example of

Survey. A local news station wants to know what percentage of people favor investing in new public light-rail system for the city. They conduct a survey, calling homes between 10:00 a.m. and 3:00 p.m. Explain why this sampling plan is biased.

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.)