Exam 11: Experiments and Observational Studies

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 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.

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 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 treatments.

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.

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 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.

An examination of the medical records of 10,000 women who died between 1990 and 2000 showed that those who had taken steroids had a higher risk of osteoporosis.Identify the parameter of interest.

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.

A new type of pain reliever is administered to 30 consenting post-operative patients in various hospitals.Although the pain reliever has already been tested for safety and effectiveness,this experiment is to observe and categorize any side-effects.Because of maturity and body mass,it is decided to test the adults separately from the children. The grouping of the adults separate from the children is an example of what?

Researchers reported that for men,being unmarried increases the risk of depression.These findings were based on the medical records of 400 married men and 500 unmarried men.Since there is no random assignment,this conclusion is not justified because there may be lurking variables.Which of the following are possible lurking variables? I: Rate of depression II: Income III: Type of employment IV: Age V: Gender

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.Determine the nature and scope of the conclusion the study can reach.

In a clinical trial,each participant will receive a placebo,a low dosage of a drug,or a high dosage of the drug.The participants consist of 90 men and 90 women.The 90 men are randomly divided into three groups of 30.Each group of men is randomly assigned to a different treatment (placebo,low dose,or high dose).Likewise,the 90 women are randomly divided into three groups of 30.Each group of women is randomly assigned to a different treatment (placebo,low dose,or high dose).Is this a completely randomized design or a randomized block design? Explain your answer.

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 20. Students who studied with Felix using method B achieved the highest scores. The person evaluating the results does not know which teacher or teaching method the students were assigned to.

Among a group of 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.

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.

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

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.Design an experiment to test the conjecture.Be sure to identify the factors,the levels,treatments,and response variable.

A clothing manufacturer is curious if celebrity endorsements will influence a customer's decision in buying its products.This clothing manufacturer premieres its latest series of commercials privately to two separate groups of potential shoppers.One group will see a series of commercials without celebrities,and one group will see a series of commercials with celebrities.Furthermore,the manufacturer decides to split up the male shoppers from the female shoppers. Grouping the shoppers together by gender is an example of what?

400 patients suffering from chronic back pain were randomly assigned to one of two groups.Over a four-month period,the first group received acupuncture treatments and the second group received a placebo.Patients who received acupuncture treatments improved more than those who received the placebo.

A researcher would like to compare the effectiveness of two competing study courses both of which claim to raise students' SAT scores.He would also like investigate whether students can benefit from listening to a certain type of music while they study.Design an appropriate experiment.Be sure to identify the factors,levels,treatments,and response variable.