Chapter 4 Anwsers
The potential for lurking variables to affect the results is
less in an experimental study than in an observational study
Identify which type of sampling is used. A market researcher randomly selects 500 people from each of 10 randomly selected cities.
Cluster random sample
Identify which type of sampling is used. To avoid working late, a quality control analyst simply inspects the first 100 items produced in a day.
Convenience sample
A swim team must select among four assistant coaches to accompany the team to an upcoming swim meet. What is the chance that a particular sample of size 2 will be selected?
0.17
A swim team must select two of its four assistant coaches to accompany the team to an upcoming swim meet. What is the chance that assistant coach C attends the meet?
0.5
Provide an appropriate response. A college employs 85 faculty members. Without replacement, select the numbers of the five members who will serve on the tenure committee next year using the random numbers given below.
16, 34, 69, 38, 13
Provide an appropriate response. After a hurricane, a disaster area is divided into 200 equal grids. Thirty of the grids are selected and every occupied household in the grid is interviewed to help focus relief efforts. Select the numbers of the first five grids that belong to the sample using the random numbers given below.
163, 169, 15, 92, 97
The manager of a natural foods grocery is considering the addition of a play area and would like to know what percentage of its customers shop with children under the age of 8. To obtain an estimate of this percentage, one morning between 9:00 and 11:00 the cashiers record how many of their customers have children under the age of 8 with them. What type of sample does this represent?
A convenience sample
A double-blind experiment of an allergy medication is being tested on 100 participants according to the following diagram:v The investigator would like to have a control group. If Group 2 receives a full dose of the medication, what should Group 1's treatment consist of?
A placebo
Which of the following is a reason to use randomization?
All of these
Identify the specified elements of the experiment. 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 RESPONSE VARIABLE
Change in diastolic blood pressure
Identify the study as observational or experimental. A researcher wished to assess the importance of exercise in weight-loss programs. 412 people, all considered to be at least 20 pounds overweight, volunteered to participate in a study. The participants 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 was calculated for each group and it was found that the average weight loss for the second group was significantly greater than the average weight loss for the first group.
Experimental
Identify the study as observational or experimental. 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 the 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 average change in blood pressure was calculated for each of the three groups and the three averages were compared.
Experimental
Identify the study as observational or experimental. Twenty volunteers who suffer from sleep apnea are randomly divided in half so that ten receive a new medication to reduce snoring while the remaining ten receive a placebo that looks like the medication. The volunteers are unaware of which group they are in and are observed at a sleep clinic overnight.
Experimental
In an experimental study, CATAGORIGAL explanatory variables are often referred to as
Factors
A sample survey is a type of experimental study.
False
An observational study assigns each subject to a treatment and then observes the response.
False
Identify the flaw(s) in the experiment or study described. 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?
II, III, IV
Identify the bias. A magazine publisher mails a survey to every subscriber asking about the quality of its subscription service. From which of the following is this study most likely to suffer?
Nonresponse bias
Explain whether an experiment or an observational study would be more appropriate to investigate whether women are more likely than men to suffer from anxiety.
Observational study; gender cannot be assigned as a treatment.
Explain whether an experiment or an observational study would be more appropriate to investigate whether a low-calorie diet can increase longevity.
Observational study; it would be unethical to subject people to a low-calorie diet over a long period of time.
The members of a board of directors have the following roles: President (P), Vice President(V), Secretary (S), Treasury(T), and Fundraiser(F) Consider these board members to be a population of interest. List the 10 possible samples (without replacement) of size two from this population of five board members.
PV, PS, PT, PF, VS, VT, VF, ST, SF, TF
Identify the specified elements of the experiment. 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 experimental 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 TREATMENT
Placebo, low drug dosage, high drug dosage
Identify type of observational study-Retrospective or Prospective Among a group of married women who were tracked for ten years, those who worked full time were more likely to divorce than those who did not work full time.
Prospective observational study
Identify type of observational study-Retrospective or Prospective 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.
Retrospective observational study
Identify the bias. The manager of a natural foods grocery is considering the addition of a play area and would like to know what percentage of its customers shop with children under the age of 8. To obtain an estimate of this percentage, one morning between 9:00 and 11:00 the cashiers record how many of their customers have children under the age of 8 with them. Which of the following is this survey likely to suffer from?
Sampling Bias
Identify the bias. A bottling company would like to estimate the proportion of its daily production (5000 cases) that meets the appropriate filling guidelines. To do so, the last 5 cases filled in the day are chosen and all of the bottles within these corresponding 5 cases are checked against the guidelines. From which, if any, of the following is this sample likely to suffer?
Sampling bias
Identify the bias. Inside the boxes of a new brand of cereal is a short survey that can be mailed back for free to the manufacturer. The survey asks the consumer if he or she likes the cereal or not. What, if any, will be the most noticeable bias for this survey?
Sampling bias
Identify which type of sampling is used. A lobbyist for a major airspace firm assigns a number to each legislator and then uses a computer to randomly generate ten numbers. The lobbyist contacts the legislators corresponding to these numbers. What sampling technique was used?
Simple random sample
The name of each contestant is written on a separate card, the cards are placed in a bag, and three names are picked from the bag.
Simple random sample
Identify which type of sampling is used. A market researcher selects 500 drivers under 30 years of age and 500 drivers who are 30 years of age and older. (2 groups)
Stratified random sample
Identify which type of sampling is used. Based on 12,500 responses from 42,000 questionnaires sent to its alumni, a major university estimated that the annual salary of its alumni was $96,500 per year. What sampling technique is used?
Survey Sample
A magazine publisher mails a survey to every subscriber asking about the timeliness of its subscription service. The publisher finds that only 5% of the subscribers responded. This 5% represents what?
The Sample
Identify the specified elements of the experiment. 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 experimental units.
The participants in the experiment
In an experimental study, the subjects are often referred to as the
experimental units
An experimental study gives the researcher more control over outside influences.
True
It is not possible to establish cause and effect definitively with observational studies.
True
Identify the flaw(s) in the experiment or study described. 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 made unaware of which group the patients were in. Identify the most serious flaw in this experiment.
Volunteers chose their treatment instead of being randomly assigned to one of the groups.
Which method of sampling is preferable if a reliable sampling frame is not available, or the cost of selecting a simple random sample is excessive?
cluster random sampling
When neither the subject nor those having contact with the subject know the treatment assignment, the study is called
double-blind.
In an experimental study, a treatment that has no active ingredients is called
placebo
The process of assigning several experimental units to each treatment is called
replication
A(n) ____________________ of n subjects from a population is one in which each possible sample of that size has the same chance of being selected.
simple random sample
Select the most appropriate answer. A method of sampling which divides the population into separate groups and then selects a simple random sample from each group is called ____________________.
stratified random sampling
