Exam 12: Experiments and Observational Surveys

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 will then be compared.The researchers will have the technicians administering the medication blinded to whether patients receive a low dose,a high dose,or a placebo.Identify the most serious flaw in this experiment.

A manufacturer of tennis rackets has designed a new racket and would like to compare it to their previous design.Suggest an appropriate experiment.

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?

An examination of the medical records of 10,000 women showed that those who were short and fair skinned had a higher risk of osteoporosis.

An educational researcher used school records to determine that,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.

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.

780 patients suffering from high blood pressure were randomly assigned to one of three groups.Over a four-month period,the first group received an experimental drug,the second group received a placebo,and the third group received no treatment.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 drug.

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.

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.

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 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.

A researcher would like to investigate whether people suffering from insomnia can be helped by taking regular yoga classes or by reducing their intake of caffeine.Design an appropriate experiment.Be sure to identify the factors,levels,treatments,and response variable.

A statistics instructor 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 60 volunteer statistics students. Volunteers will be randomly assigned to one of two groups.Group 1 will be taught the statistics course using method A and group 2 will be taught using method B.Other than the different methods,everything else will be similar for the two groups.For example,both groups will have the same teacher,the same lecture room,the same amount of time devoted to the course.At the end of the semester,students will all take the same test.Then the scores for the two groups will be compared.If the first group has a mean score of 67.7 with a standard deviation of 13.4 and the second group a mean score of 71.6 with a standard deviation of 11.2,do you think that this result is statistically significant? Explain.

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.

780 participants suffering from depression 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.At the end of the period each participant rated their mood on a scale of 1-10.Identify the factor(s)in the experiment and the number of levels for each.

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.The 30 plants which are planted on the shady side are randomly assigned to one of three groups.The first group are grown with no fertilizer,the second group with a small amount of fertilizer,and the third group with a large amount of fertilizer.The 30 plants which are planted on the sunny side are likewise randomly assigned to one of three groups.The first group are 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.

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.Identify the flaw(s)in this experiment and suggest a way of improving the experiment.

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.

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.

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.Identify the factor(s)in the experiment and the number of levels for each.