Question 1

A researcher tests a new intervention for nausea associated with chemotherapy in hospitalized patients. The researcher does not want to suggest nausea to the patients, so as the dependent variable, the researcher uses the answer the patients give to the question, "How are you feeling this morning?" This is a threat to which type of validity?

Accepted Answer

The question "How are you feeling this morning?" is too vague and does not specifically measure the construct of interest, which is nausea. This threatens construct validity because it's unclear if the measurement accurately reflects the concept (nausea) the researcher intends to study.

Question 2

A researcher tests a new intervention for nausea associated with chemotherapy, in hospitalized patients. At the same time, a new over-the-counter medication containing natural herbs is marketed aggressively, and some of the hospital patients are given this herbal remedy by their families. This is a threat to which type of validity?

Accepted Answer

A

Question 3

A researcher is comparing a new and less expensive treatment with an established treatment, in hopes of showing that there is no difference in outcome. The researcher does not perform a power analysis and, consequently, selects a sample size that is smaller than what would be recommended for an analysis of variance. The results show that there is a significant difference in outcome between the two treatments, and that the new treatment has poorer outcomes. What is the negative result of the researcher's decision to use a smaller sample?

Accepted Answer

B

Question 4

The researcher divides his lab rats into two groups and administers IV methamphetamine to one of the groups, in order to determine its effect on the fear-flight response. This is an example of which of the following?

Accepted Answer

Manipulation is the correct answer because the researcher is actively changing a variable (administering IV methamphetamine) to observe its effect on another variable (the fear-flight response), which is a hallmark of experimental design.

Question 5

A researcher conducts interventional research and uses a small sample that is not randomly selected. When the researcher replicates the study, twice, the researcher again uses the same site and another small sample that is not randomly selected. This is a threat to which type of validity?

Accepted Answer

The use of small, non-randomly selected samples and the replication of the study at the same site with similar samples threaten external validity. This is because the findings may not be generalizable to a broader population, as the samples do not represent the larger group outside of the study's specific context.

Question 6

A researcher measures the dependent variable in an interventional group of subjects both before and after an intervention. The researcher also measures the same dependent variable in a non-interventional group, at the same two points in time. The groups are not randomly assigned. What kind of design is this?

Accepted Answer

This is a pretest-posttest design with a comparison group because it involves measuring the dependent variable in both the interventional and non-interventional groups before and after the intervention, but without random assignment of participants to groups.

Question 7

A group of 25 Labrador retrievers, and their owners, are brought to the research lab, one at a time. The Labrador retrievers are shown various stimuli, including a squirrel that runs along a wire at the top of the lab, to elicit barking. Then the owners command the dogs to stop barking, and the stimulus is repeated. The duration of barking is measured. Then the owners are taught a different technique for quieting their barking dogs. A week later, the dogs and their owners return to the lab, the stimuli are introduced, and the duration of barking is measured. This is an example of what type of design?

Accepted Answer

This study involves measuring the duration of barking before and after the owners are taught a new technique, without a comparison group, making it a one-group pretest-posttest design.

Question 8

A researcher is comparing a new and less expensive treatment with an established treatment, in hopes of showing that there is no difference in outcome. The researcher does not perform a power analysis and, consequently, selects a sample size that is smaller than what would be recommended for an analysis of variance. The results show that there is no significant difference in outcome between the two treatments. Which type of validity is affected by this?

Accepted Answer

Statistical conclusion validity is affected because the small sample size, due to the lack of power analysis, increases the risk of Type II error (failing to detect a difference when one actually exists), directly impacting the accuracy of statistical conclusions.

Question 9

A study using the factorial design measures the effect upon hemoglobin levels of four independent variables, each administered randomly and independently. How many distinct groups are there in this factorial design?

Accepted Answer

In a factorial design, the number of distinct groups is determined by multiplying the levels of each independent variable. If there are four independent variables and each is administered independently (assuming each has at least two levels), the minimum number of distinct groups is 2^4 = 16.

Question 10

A researcher uses matching to constitute a control group, while performing a study on psychotherapy as an adjunct treatment for substance addiction. What type of validity might be enhanced by matching, in this instance?

Accepted Answer

Matching participants in the experimental and control groups helps to ensure that the groups are equivalent on certain variables, which reduces confounding variables and enhances the internal validity of the study. This makes the results more likely to be due to the intervention rather than differences between the groups.

Question 11

John Stuart Mill insisted that in order for causation to be demonstrated, there must be no alternative explanation for why a change in one variable leads to a change in the other variable. This concept of alternative explanations is the idea that underlies which type of validity?

Accepted Answer

John Stuart Mill's emphasis on the elimination of alternative explanations for a change in variables directly relates to internal validity. Internal validity is concerned with the extent to which a causal relationship can be established between two variables, without the influence of extraneous variables.

Question 12

What is the essential difference between a control group and a comparison group?

Accepted Answer

A control group is specifically designed to control for the effects of extraneous variables, allowing researchers to isolate the effect of the independent variable. A comparison group, on the other hand, may not control for these variables as rigorously.

Question 13

Subjects in a multiple group experimental study are tested for how much time it takes them to navigate a maze and find the chocolate. The maze is reconstructed after each run, and three different floor plans are used. Each group is tested eight times in 8 hours at a different time of day. The runs later in the day have faster times than the earlier ones. Which threat to internal validity might account for this difference?

Accepted Answer

Testing effects might account for this difference because the subjects are likely becoming more familiar with the task over time, which could lead to faster completion times. This is a common issue in studies where participants are tested multiple times.

Question 14

Nurses who provide discharge teaching to patients after colonoscopy call these patients the day after the procedure to check on their status. At that time, patients who have had polyps removed invariably ask how long it will be until they receive their results. The nurses decide to design a study in which they will change their discharge teaching, in order to include information about the time frame for biopsy results. The nurses then will measure patient satisfaction results, comparing them with the results for the previous month, before the change. Which type of research design will they use?

Accepted Answer

The nurses are implementing a change (including information about the time frame for biopsy results in their discharge teaching) and then measuring the effect of this change on patient satisfaction. This involves manipulating an independent variable (the discharge teaching content) and measuring its effect on a dependent variable (patient satisfaction), without random assignment to groups, which is characteristic of a quasi-experimental design.

Question 15

Hospital nurses are observed in order to determine exactly how long they swab IV ports with alcohol. Because they are being observed, they "scrub the hub" longer than they ordinarily would have. This is an example of what concept relevant to quantitative research?

Accepted Answer

This is an example of the Hawthorne effect, which occurs when individuals modify an aspect of their behavior in response to their awareness of being observed.

Question 16

Identify the study design used in the following research project:
Twenty patients, all of whom have bipolar mania, have been placed on lithium and also begun on a medication believed to prevent rapid cycling. The patients are followed for 12 months, at which time they are seen by a psychiatrist monthly, to adjust their dosages. Medication compliance, emergency department visits, and mental health hospitalizations are measured. These are compared with another group of patients with the same mental illness, being treated on lithium alone. What is this design?

Accepted Answer

The answer of Identify the study design used in the...

Question 17

A study's hypothesis that a new surgical approach produces safer outcomes in immunosuppressed patients is tested in a 14-site research study across the United States. Subjects at all sites are randomly selected and randomly assigned to experimental versus control groups. What strategy is used in this research project?

Accepted Answer

The strategy used in this research project is a Randomized-controlled trial (RCT). In an RCT, subjects are randomly assigned to either the experimental group receiving the intervention being tested or to a control group. This method is considered the gold standard for testing the efficacy of new treatments or interventions because it minimizes bias and ensures that any differences observed between the groups are likely due to the intervention itself rather than other factors.

Question 18

The essentialists insisted that a cause be necessary and sufficient for an effect to occur. In a modern study, alcohol dependency is found to lead eventually to permanent liver damage, except when the person with alcoholism consumes a diet plentiful in the B- vitamins. In addition, liver damage can emerge in the absence of alcohol dependency. What would the essentialists say about the causative relationship between alcohol dependency and liver damage?

Accepted Answer

The essentialists would argue that alcohol dependency is neither necessary nor sufficient for liver damage because liver damage can occur without alcohol dependency and alcohol dependency does not always lead to liver damage if the person consumes a diet rich in B-vitamins.

Question 19

Immediately after the intervention in an experimental study of the negative effects of smoking tobacco, the state tax on cigarettes increases the cost from $4 to $8 per pack. Which threat to internal validity does this pose?

Accepted Answer

The increase in the state tax on cigarettes is an external event that occurred during the experiment, which could influence the study's outcomes independently of the intervention being tested. This is an example of a history threat to internal validity, as it involves specific events occurring between the first and second measurements that are not part of the manipulation.

Question 20

If a one-group pretest-posttest study uses subjects as their own controls, which is the study design?

Accepted Answer

A one-group pretest-posttest study where subjects serve as their own controls is considered a quasi-experimental design because it lacks random assignment of participants to experimental and control groups.

Quiz 11: Quantitative Methodology: Interventional Designs and Methods