Chapter 5Chapter 5

ReviewReview

The Mayor of Port Orange wants to know what The Mayor of Port Orange wants to know what the residents think of a proposed policy to the residents think of a proposed policy to change the billing of utilities in the area. His change the billing of utilities in the area. His staff reports that 300 letters have been staff reports that 300 letters have been received on the matter, of which 219 oppose received on the matter, of which 219 oppose changing the current billing method. What is changing the current billing method. What is the population in this situation?the population in this situation?

A.A. 300 letters received300 letters received

B.B. 219 opposing the change in the billing method219 opposing the change in the billing method

C.C. The residentsThe residents

What do we call a sample that consists What do we call a sample that consists of the entire population?of the entire population?

A.A. A censusA census

B.B. A stratumA stratum

C.C. A big mistakeA big mistake

Which of the following is a method for Which of the following is a method for improving the accuracy of a sample?improving the accuracy of a sample?

A.A. Use smaller sample sizesUse smaller sample sizes

B.B. Use no more than 5 or 6 words in any Use no more than 5 or 6 words in any question.question.

C.C. Use computerized dialing whenever Use computerized dialing whenever possible to avoid human interviewers.possible to avoid human interviewers.

D.D. Use large sample sizes.Use large sample sizes.

A design is biased if which of the A design is biased if which of the following is true?following is true?

A.A. Placebos have been used.Placebos have been used.

B.B. Systematic favoritism in outcomes.Systematic favoritism in outcomes.

C.C. A sexual or racial preference is A sexual or racial preference is suspected.suspected.

Why are control groups used in Why are control groups used in experiments?experiments?

A.A. To ensure all participate equally.To ensure all participate equally.

B.B. To guarantee others than the To guarantee others than the investigators, who have a vested interest investigators, who have a vested interest in the outcome, control how the in the outcome, control how the experiment is conducted.experiment is conducted.

C.C. To minimize the effects of lurking To minimize the effects of lurking variables i.e. placebo effect.variables i.e. placebo effect.

Suppose the NewsJournal asks a sample of Suppose the NewsJournal asks a sample of 250 Volusians their opinion on property 250 Volusians their opinion on property taxes in Volusia County.taxes in Volusia County.

• Is this study an experiment? Why or why Is this study an experiment? Why or why not? not? No. A treatment isn’t imposedNo. A treatment isn’t imposed• What is the sample for this opinion poll? What is the sample for this opinion poll? 250 Volusians250 Volusians

• What is the population? What is the population? All VolusiansAll Volusians

Vitamin E may have special health benefits

Large doses of vitamin E apparently can reduce harmful side effects of bypass surgery in heart patients. A study involving 28 bypass patients found that the 14 patients who took vitamin E for two weeks before their operations had significantly better heart function after the procedure than the 14 patients who took placebos. The vitamins apparently prevent damage to the heart muscle by destroying the toxic chemicals, called free radicals, that form when blood is cut off during the surgery, said Dr. Terrance Yau of the University of Toronto.

• Does the article on Vitamin E describe an Does the article on Vitamin E describe an experiment? Explain. experiment? Explain. Yes, treatment imposed.Yes, treatment imposed.• Describe the experimental units/subjects Describe the experimental units/subjects used. used. How many were there? How many were there? 28 bypass patients28 bypass patients• Identify the explanatory variable (s). Identify the explanatory variable (s). Medication Medication givengiven• How many treatments were there? List How many treatments were there? List them. them. 2 – Vitamin E and a placebo2 – Vitamin E and a placebo• How many participants are in each treatment How many participants are in each treatment group? group? 14 14 • Identify the response variable. Identify the response variable. Heart function Heart function (better) after the procedure.(better) after the procedure.

Using line 125 of your Random Numbers Using line 125 of your Random Numbers Table (RNT), select the first five students in Table (RNT), select the first five students in a simple random sample (SRS) of 20 a simple random sample (SRS) of 20 students. students. Alphabetize the 500 students and Alphabetize the 500 students and assign the numbers 000-499 ignoring 500 – assign the numbers 000-499 ignoring 500 – 999 in my RNT. 461, 214, 235, 119, 033999 in my RNT. 461, 214, 235, 119, 033

Suppose there are 500 students in Suppose there are 500 students in the Senior Class of 2007the Senior Class of 2007

Bias is present in each of the following Bias is present in each of the following sampling designs. In each case, identify the sampling designs. In each case, identify the type of bias involved and state whether you type of bias involved and state whether you think the sampling frequency obtained is think the sampling frequency obtained is lower or higher than the actual population lower or higher than the actual population parameter.parameter.

Types of Biases Types of Biases - Undercoverage – Undercoverage – Groups are left outGroups are left out- Nonresponse – Nonresponse – chosen and cannot be reached/refuses to cooperatechosen and cannot be reached/refuses to cooperate- Wording of questions – Wording of questions – too technical/filled with jargontoo technical/filled with jargon

A pollster seeks information about the A pollster seeks information about the proportion of American adults that oppose proportion of American adults that oppose gun controls. He asks a SRS of 100 gun controls. He asks a SRS of 100 American adults: “Do you agree or disagree American adults: “Do you agree or disagree with the following statement: Americans with the following statement: Americans should preserve their constitutional right to should preserve their constitutional right to keep and bear arms.” A total of 91 or 91%, keep and bear arms.” A total of 91 or 91%, said, “agree”. said, “agree”. Wording of Question. Wording of Question. Sampling is higher than the population Sampling is higher than the population parameter. parameter.

A chocolate company in Hershey wants to A chocolate company in Hershey wants to know what percentage of local households know what percentage of local households make chocolate chip cookies at least twice a make chocolate chip cookies at least twice a week. A company representative calls 500 week. A company representative calls 500 households during the daytime and finds households during the daytime and finds that 50% of them make cookies at least that 50% of them make cookies at least twice a week. twice a week. Nonresponse – households Nonresponse – households have been chosen, but some folks are have been chosen, but some folks are working. Sampling parameter is higher than working. Sampling parameter is higher than the population parameter.the population parameter.

It is believed that 80% of all students use their lockers daily. It is believed that 80% of all students use their lockers daily.

• Describe how you would simulate a SRS of 10 students. Describe how you would simulate a SRS of 10 students. To simulate the To simulate the 80% which would constitute a success, I would assign the numbers 0 – 7 for 80% which would constitute a success, I would assign the numbers 0 – 7 for using their locker, l. Assign 8 and 9 for non use of locker (failure), n. Beginning using their locker, l. Assign 8 and 9 for non use of locker (failure), n. Beginning at line 127, I would select one digit at a time until I get 10 digits which would at line 127, I would select one digit at a time until I get 10 digits which would represent the 10 students. I would record my findings and then compare. represent the 10 students. I would record my findings and then compare.

• Beginning at line 127, actually simulate a SRS of 10 students. Beginning at line 127, actually simulate a SRS of 10 students. •4, 3, 9, 0, 9, 9, 9, 4, 7, 74, 3, 9, 0, 9, 9, 9, 4, 7, 7•l, l, n, l, n, n, n, l. l. l Use locker – 6; non use of locker 4l, l, n, l, n, n, n, l. l. l Use locker – 6; non use of locker 4

• What is the proportion of students in the sample who use their lockers daily?What is the proportion of students in the sample who use their lockers daily?

•6/10 = 60% 6/10 = 60%

Turkeys raised commercially for food are often fed Turkeys raised commercially for food are often fed the antibiotic salinomycin to prevent infections the antibiotic salinomycin to prevent infections from spreading among the birds. However, from spreading among the birds. However, salinomycin can damage the birds' internal organs, salinomycin can damage the birds' internal organs, especially the pancreas. A researcher believes especially the pancreas. A researcher believes that a combination of selenium and vitamin E in that a combination of selenium and vitamin E in the birds' diet may prevent injury. He wants to the birds' diet may prevent injury. He wants to explore the effects of two different dosages of explore the effects of two different dosages of selenium (call them S1, S2) in combination with selenium (call them S1, S2) in combination with any of three different dosages of vitamin E (call any of three different dosages of vitamin E (call them E1, E2, E3) added to the turkeys' diets. them E1, E2, E3) added to the turkeys' diets. There are 48 turkeys available for the study. At There are 48 turkeys available for the study. At the end of the study, the birds will be killed and the the end of the study, the birds will be killed and the condition of their pancreas examined with a condition of their pancreas examined with a microscope.microscope.

Outline in diagram form an appropriate design for this experiment. In your Outline in diagram form an appropriate design for this experiment. In your diagram, indicate how many turkeys are assigned to each treatment group. diagram, indicate how many turkeys are assigned to each treatment group. Discuss how you would assign the turkeys to the first treatment group.Discuss how you would assign the turkeys to the first treatment group.

Random Assignment

01 – 48(The ABCs aren’t

necessary)

Treatment 1S1E1

8 turkeys

Treatment 1S1E2

8 turkeys

Treatment 3S1E3

8 turkeys

Treatment 4S2E1

8 turkeys

Treatment 5S2E2

8 turkeys

Treatment 6S2E3

8 turkeys

Compare

Examine the turkeys before diet change. First 8 turkeys will be assigned to group 1, the 2nd set of 8 to group 2, and etc until all turkeys are placed in a group. After a period of time the turkeys

will be killed and their pancreas examined.

Chapter 5 TestChapter 5 Test

Good luck on the test Good luck on the test