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Exam 11: Experiments and Observational Studies

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Question 41

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A medical researcher believes that supplements of glucosamine can help to reduce the pain of arthritis.She designs an experiment as follows.She will obtain a group of volunteers who suffer from arthritis.Each patient's condition will be evaluated by a doctor at the start of the experiment.Volunteers will be randomly assigned to one of three groups.Each day patients in group 1 will receive a low dose of glucosamine,patients in group 2 a higher dose of glucosamine,and patients in group 3 a placebo.After a suitable amount of time,for example two months,the doctor will evaluate each patient's progress.Based on the amount of inflammation and the patient's report on the amount of pain,the doctor will give each patient a numerical score to represent their improvement.The researcher will then compare the improvement for the three groups.The evaluating doctor will be blinded to patients' treatments.If the result is found to be statistically significant,what would that mean in this case?

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The difference in the amount o...

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Question 42

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An ice cream company wants to introduce a new flavor.They are considering two possibilities - Mint Delight and Chocolate Fiesta.They want to know which one customers will prefer.Design an experiment to investigate this question.The company feels that children may have different preferences than adults.Be sure to take that into account in the design of the experiment.

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Answers may vary.Obtain a group of volun...

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Question 43

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A nutritionist has come up with a new diet that she believes will allow overweight people to lose weight more quickly than the diet she had previously prescribed for patients.She suspects that the new diet may be more effective for women than for men.Design an appropriate experiment.

An educational researcher used school records to determine that in the year 2000 in one school district,84% of children living in two-parent homes graduated high school while 75% of children living in single-parent homes graduated high school.Determine the parameter of interest.

At a hospital in 1998,674 women were diagnosed with breast cancer.Five years later,88% of the Caucasian women and 83% of the African American women were still alive.A researcher concludes that being Caucasian causes women with breast cancer an increased chance of surviving five years.Why is this conclusion not justified?

An education researcher wishes to assess the effectiveness of three different methods for teaching young children to read.The 380 children participating in the study are divided into three groups.The study runs for six months.The children in the first group are taught using method A,the children in the second group are taught using method B,and the children in the third group are taught using method C.At the end of the six months,the reading ability of the children in the different groups is assessed.Why is it important to use random assignment when dividing the children into three groups?

A researcher wants to investigate the effectiveness of a cholesterol-lowering medication.The 450 participants are first divided into two groups - those suffering from diabetes and those not suffering from diabetes.Within each group the participants are randomly assigned to one of three groups.The first group will receive a low dose of the medication,the second group will receive a high dose of the medication,and the third group will receive a placebo.At the end of a six-month period,each person's cholesterol will be tested and the change in their cholesterol level will be recorded.Identify the treatments.

An employer suspects that on Mondays the percentage of employees absent from work is higher than on other days.Design a way he could find out whether there is any merit to his belief.Should he use an experiment or an observational study? He would like to have the information as soon as possible.

A researcher wants to investigate whether different forms of exercise can be used to help hyperactive children.A group of 90 children is divided into two groups according to age - those aged 9-12 and those aged 5-9.Within each age group the children are randomly assigned to one of three groups.The first group will just do their normal exercise.The second group will be given an additional exercise routine (moderate) .The third group will be given an additional exercise routine (strenuous) .At the end of a four-month period,parents will be asked to evaluate their children's progress.Identify the factor(s) and any blocking variables and the number of levels for each.

780 men suffering from high blood pressure were randomly assigned to one of three groups.Over a four-month period,the first group received a low dosage of an experimental drug,the second group received a high dosage of the drug,and the third group received a placebo.The biggest decrease in blood pressure was for those who received the low dosage of the drug.Identify the subjects studied.

A researcher wants to examine the effect of fertilizer and the effect of sunlight on the yield of tomatoes.She bought 60 tomato plants at a local garden store.She randomly assigned 30 tomato plants to be planted on the sunny side of the hill and 30 to be planted on the shady side.Within each group of 30 plants,she randomly assigned plants to one of three groups.The first group is grown with no fertilizer,the second group with a small amount of fertilizer,and the third group with a large amount of fertilizer.All tomato plants are planted at the same time and are all treated alike (in terms of how much they are watered,weeded etc) .Each plant is grown to maturity.The total weight of tomatoes obtained from each plant is recorded.The person evaluating the results does not know which tomatoes received fertilizer or which were grown on the sunny side.Within both groups (those grown on the sunny side and those grown on the shady side) tomatoes grown with a large amount of fertilizer yielded the most tomatoes.Determine the nature and scope of the conclusion the experiment can reach.

A medical researcher believes that supplements of glucosamine can help to reduce the pain of arthritis.She would like to test the supplement at two different dosage levels.She designs an experiment as follows to test her conjecture.She will obtain a group of volunteers who suffer from arthritis.Each patient's condition will be evaluated by a doctor at the start of the experiment.Volunteers will be randomly assigned to one of two groups.Each day for the duration of the experiment,patients in group 1 will receive a low dose of glucosamine,patients in group 2 will receive a higher dose of glucosamine.After a suitable amount of time (two months,for example) ,the doctor will evaluate each patient's progress.Based on the amount of inflammation and the patient's report on the amount of pain,the doctor will give each patient a numerical score to represent their improvement.The amount of improvement for the two groups would then be compared.She will have the evaluating doctor and the technicians administering the supplements blinded to whether patients receive a low dose or high dose.Identify the most serious flaw in this experiment.

A pharmaceutical company has developed a medication which they believe will help to reduce the pain of arthritis.They would like to test the medication at two different dosage levels.They design an experiment as follows to test the medication.They will obtain a group of volunteers who suffer from arthritis.A doctor from the pharmaceutical company will evaluate each patient's condition at the start of the experiment.Volunteers will be randomly assigned to one of three groups.Each day for the duration of the experiment,patients in group 1 will receive a low dose of the medication,patients in group 2 will receive a higher dose of the medication,and patients in group 3 will receive a placebo.After a suitable amount of time (two months,for example),the same doctor will evaluate each patient's progress.Based on the amount of inflammation and the patient's report on the amount of pain,the doctor will give each patient a numerical score to represent their improvement.The amount of improvement for the three groups would then be compared.They will also ensure that the technicians administering the supplements are blinded to whether patients receive a low dose,a high dose,or a placebo.Identify the flaw(s)in this experiment.

A double-blind experiment of an allergy medication is being tested on 100 participants according to this diagram: If Group 2 receives a full dose of the medication,what should Group 1's treatment consist of?

A researcher wants to investigate whether different forms of exercise can be used to help hyperactive children.A group of 90 children is divided into two groups according to age - those aged 9-12 and those aged 5-9.Within each age group the children are randomly assigned to one of three groups.The first group will just do their normal exercise.The second group will be given an additional exercise routine (moderate) .The third group will be given an additional exercise routine (strenuous) .At the end of a four month period parents will be asked to evaluate their children's progress.

In a clinical trial,780 participants suffering from high blood pressure were randomly assigned to one of three groups.Over a one-month period,the first group received a low dosage of an experimental drug,the second group received a high dosage of the drug,and the third group received a placebo.The diastolic blood pressure of each participant was measured at the beginning and at the end of the period and the change in blood pressure was recorded.The biggest decrease in blood pressure was for those who received the low dosage of the drug.

A medical researcher believes that supplements of glucosamine can help to reduce the pain of arthritis.She would like to test the supplement at two different dosage levels.She designs an experiment as follows to test her conjecture.She will obtain a group of volunteers who suffer from arthritis.Each patient's condition will be evaluated by a doctor at the start of the experiment.Volunteers will be randomly assigned to one of two groups.Each day for the duration of the experiment,patients in group 1 will receive a low dose of glucosamine and patients in group 2 will receive a higher dose of glucosamine.After a suitable amount of time (two months,for example),the doctor will evaluate each patient's progress.Based on the amount of inflammation and the patient's report on the amount of pain,the doctor will give each patient a numerical score to represent their improvement.She would then compare the amount of improvement for the two groups.Also,she will ensure that the evaluating doctor and the technicians administering the supplements are blinded to whether patients receive a low dose or high dose.Identify the flaw(s)in this experiment.

A medical researcher designs an experiment to test whether supplements of glucosamine can help to reduce the pain of arthritis.She will obtain a group of 90 volunteers who suffer from arthritis.Each patient's condition will be evaluated by a doctor at the start of the experiment.Volunteers will be randomly assigned to one of three groups.Each day patients in group 1 will receive a low dose of glucosamine,patients in group 2 will receive a higher dose of glucosamine,and patients in group 3 will receive a placebo.After a suitable amount of time,the doctor will evaluate each patient's progress.Based on the amount of inflammation and pain,the doctor will give each patient a numerical score to represent their improvement.The researcher will then compare the improvement for the three groups.Describe a strategy to randomly assign the 90 volunteers to the three treatments.

A researcher would like to investigate whether people suffering from insomnia can be helped by taking yoga classes.She designs an experiment as follows.She will obtain a group of volunteer insomniacs who do not currently practice yoga.Each person's degree of insomnia at the start of the experiment will be evaluated.Volunteers will be randomly assigned to one of three groups.Those in group 1 will practice yoga every day,those in group 2 will practice 3 times per week,and those in group 3 will not practice yoga.At the end of a suitable time period each person's degree of insomnia will again be evaluated.The improvement for the three groups will then be compared.Explain why it is important to assign volunteers to groups at random rather than letting them choose their own group.

An educational researcher has designed two different methods for teaching a statistics course and would like to investigate which is more effective.He designs an experiment as follows.He will obtain a group of volunteer statistics students.Volunteers will be randomly assigned to one of two groups.Group 1 will be taught the statistics course by Anna Clark using method A and group 2 will be taught by Bob Beauman using method B.At the end of the semester,students will all take the same test.Then the scores for the two groups will be compared.The person grading the tests will be blinded to which group students were in.Identify the most serious flaw in this experiment.