Exam 12: Experiments and Observational Surveys

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.

A researcher wished to assess the importance of exercise in weight-loss programs.412 people,all considered to be at least 20 pounds overweight,were randomly assigned to one of two groups.Over a two-month period,the first group followed a particular diet but were instructed to perform no exercise other than walking.The second group followed the same diet but also performed aerobic exercise for one hour each day.At the end of the two months,the weight loss of each participant was recorded.The average weight loss for the second group was greater than the average weight loss for the first group.

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.

An education researcher was interested in examining the effect of the teaching method and the teacher on students' reading levels.257 students participated in an experiment.There were two different teachers (Juliana and Felix)and three different teaching methods (A,B,and C).Students were randomly assigned to a teaching method and teacher.At the end of the semester the students took a reading test on which they received a score out of 4.Students who studied with Felix using method B achieved the highest scores.Identify the number of treatments and list them.

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?

Explain the difference between an observational study and an experiment.

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 education researcher was interested in examining the effect of the teaching method and the teacher on the reading level of students with learning disabilities.257 students with learning disabilities participated in an experiment.There are four different teachers (Juliana,Felix,Sonia,and Helen)and three different teaching methods (A,B,and C).Students are randomly assigned to a teaching method and a teacher.Those who studied with Sonia using method B achieved the highest scores on a reading test.Identify the subjects studied.

A manufacturer of tennis rackets has designed a new racket and would like to investigate whether players will prefer it to their previous design.The company obtains 100 volunteer tennis players.Volunteers are randomly assigned to one of two groups.Group 1 will use the company's previous racket first and the new racket second.Group 2 will use the new racket first and the company's previous racket second.Each player will serve 30 times with each racket.Then the percentage of good serves with the two rackets will be compared.The players are blinded to which racket they are using.Also,the person recording the percentage of good serves is blinded to which racket the players use.If the group of volunteers consists of 50 professional tennis players and 50 beginners,how could the experiment be improved?

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.Identify the levels of the factor.

An education researcher was interested in examining the effect of the teaching method and the effect of the particular teacher on students' scores on a reading test.In a study,there are four different teachers (Juliana,Felix,Sonia,and Helen)and three different teaching methods (A,B,and C).The number of students participating in the study is 258.Students are randomly assigned to a teaching method and teacher.After a four-month period,students take a reading test and are given a score out of 10.Identify the levels of the factor "teaching method".

Researchers reported that going to the gym regularly increases your chance of finding a high paying job.These findings were based on incomes reported by 200 active members of a gym and 200 people who do not belong to a gym.Why is this conclusion not justified?

Researchers reported that unmarried men are more likely to suffer from clinical depression than married men.These findings were based on the marriage histories of 700 men suffering from depression and 600 men not suffering from depression.Determine the nature and scope of the conclusion the study can reach.

An education researcher was interested in examining the effect of the teaching method and the effect of the teacher on students' scores on a reading test.Suppose there are four different teachers (Juliana,Felix,Sonia,and Helen)and three different teaching methods (A,B,and C).Students were randomly assigned to a teaching method and teacher.Those who studied with Sonia using method B achieved the highest scores.

A manufacturer of tennis rackets has designed a new racket and would like to compare it to their previous design.They design an experiment as follows.They will obtain 100 volunteer tennis players.Volunteers will be randomly assigned to one of two groups.Group 1 will use the company's previous racket first and the new racket second.Group 2 will use the company's new racket first and the previous racket second.Each player will serve 100 times with each racket.The percentage of good serves with the two rackets will then be compared.The experiment is double blind.If the group of volunteers consists of 60 professional tennis players and 40 beginners,explain why blocking by tennis level would be important.

In an experiment,explain the difference between the treatments and the factors.

Among a group of Canadian men who were tracked for ten years,those who had scored over 130 on intelligence tests were more likely to suffer severe depression than those who had scored below 130 on intelligence tests.Identify the subjects studied.

A manufacturer of tennis rackets would like to test their new racket.The company sponsors 10 tennis players who will be playing at Wimbledon.To test the racket,they have each player serve 30 times with their old racket.Then they have each player serve 30 times with the new racket.They compare the percentage of good serves with the two rackets.Identify the flaw(s)in this experiment and suggest some improvements.

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.

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 volunteers who are suffering from insomnia and who do not currently practice yoga.Each person's degree of insomnia at the start of the experiment will be evaluated.She will investigate whether yoga classes every day or three times per week are more effective.So the factor yoga will have 3 levels (no yoga,yoga three times a week,yoga every day).Each volunteer will choose which group they would like to be part of.At the end of a suitable time period,for example two months,each person's degree of insomnia will again be evaluated.The improvement for the three groups will then be compared.The person evaluating the insomnia levels will be blinded to which group the patients were in.Identify the flaw(s)in this experiment.