Question 1

One threat to the internal validity of research that affects both true experiments and quasi-experiments is

Accepted Answer

The answer of One threat to the internal validity of...

Question 2

When individuals' performance on a posttest differs from their initial testing not because of a treatment but because of familiarity with the measure,a __________ threat to internal validity is likely.

Accepted Answer

The testing threat to internal validity occurs when individuals' performance on a posttest is influenced by their familiarity with the measure due to initial testing. This is not caused by the treatment itself, but rather by the experience of taking the measure at two different points in time. Regression refers to the phenomenon where individuals' extreme scores on a pretest regress towards the mean on a posttest, and is not relevant in this scenario. Instrumentation refers to changes in the measurement instrument or procedures over time, which could also impact posttest scores but is not mentioned as a factor in the scenario. Contamination refers to the spread of treatment effects from the treatment group to the control group, which also does not apply here.

Question 3

A threat to internal validity that occurs when information about the experiment is communicated between the different groups of participants is known as

Accepted Answer

Contamination occurs when information about the experiment is communicated across different groups of participants, which can lead to participants in the control group being influenced by the intervention. This is a threat to internal validity. The other answer choices are not applicable to this scenario - novelty effects refer to the impact of something new or novel in an experiment, the Hawthorne effect refers to changes in behavior due to being observed, and the cross-communication threat is not a commonly used term in research.

Question 4

In a study of the effectiveness of a treatment for depression,a psychologist assesses patients' symptoms of depression using a reliable questionnaire both before and for several months after treatment.During the same time period,the psychologist also assesses the symptoms of individuals who are randomly assigned to a waiting-list control group.The results indicate that individuals in both groups experienced a decrease in their symptoms over the 8-month time period of the study.One threat to internal validity the researcher should consider is

Accepted Answer

Maturation is a threat to internal validity because it refers to changes in participants that occur over time, which could explain the decrease in symptoms in both groups, independent of the treatment.

Question 5

An argument for the internal validity of quasi-experiments

Accepted Answer

Quasi-experiments do not have the same level of control as true experiments, which can lead to potential threats to internal validity. However, an argument for the internal validity of quasi-experiments can be made by examining supplementary data and using logical analysis in addition to the results of the quasi-experiment itself. This allows for a more comprehensive evaluation of the study and helps to address potential threats to internal validity. It is not necessary to have a corresponding true experiment to make this argument.

Question 6

Contamination that results from communication of information between groups of participants in an experiment can lead to all of the following except

Accepted Answer

Communication of information between groups of participants may lead to resentment, rivalry, and diffusion of treatments, but it is unlikely to result in greater compliance with instructions within each group. In fact, contamination may lead to participants challenging the instructions given to them by the researchers.

Question 7

Students on two college campuses serve as treatment and control groups in a study investigating the effectiveness of an alcohol-abuse prevention campaign.A well-known student on one of the campuses dies of alcohol intoxication in the course of the study;students on the other campus did not learn of the student's death.The reaction of other students to the student's death on their campus could represent a potential threat to the internal validity of the study called

Accepted Answer

The potential threat to the internal validity of the study is the additive effects of selection and history. The death of the well-known student could impact the behavior and attitudes of students on one campus (selection), and their subsequent participation in the alcohol-abuse prevention campaign (history), which could affect the results of the study. The fact that students on the other campus did not experience the same event means that the potential threat is not just a result of selection or history alone, but the combination of both (additive effects of selection and history).

Question 8

The main problem associated with subject attrition during the course of a study is that

Accepted Answer

Subject attrition can lead to the groups no longer being equivalent, as individuals may drop out for different reasons (e.g. illness, lack of motivation). As a result, the remaining participants in each group may differ in important ways that impact the study's results.

Question 9

An intervention in an office setting leads employees to be pleased that the management is interested in their welfare.If the employees' performance improves in this situation,the researcher should be concerned about potential

Accepted Answer

The Hawthorne effect refers to the phenomenon where individuals modify their behavior simply because they know they are being observed, and this can result in improved performance. In an office setting, an intervention that shows management is interested in the welfare of employees may lead to the Hawthorne effect. Therefore, if there is an improvement in employee performance, the researcher should consider the possible influence of the Hawthorne effect. Option A (contamination effects) and Option C (selection threats to internal validity) could also be potential concerns in this scenario, but the Hawthorne effect is the most likely explanation for improved performance in response to an intervention aimed at showing concern for employee welfare. Option B (lack of discontinuity in the time series) is not relevant to this scenario.

Question 10

When people's performance changes because they are enthusiastic or energized by an intervention,the results of a study are likely affected by

Accepted Answer

Novelty effects occur when participants' performance changes due to the excitement or interest in a new intervention, rather than the intervention itself.

Question 11

The hallmark of a quasi-experiment is

Accepted Answer

Quasi-experiments are characterized by the lack of random assignment of participants to conditions, which differentiates them from true experiments.

Question 12

A high school teacher conducted a test of a new approach to teaching math.Students were given a pretest when their math class began and a posttest at the end of the semester.The students' math performance increased.The teacher learned near the end of the semester,however,that in their science classes the students were using new computer software that included much of the math the teacher covered in his course.Which of the following threats to internal validity does the new computer software represent?

Accepted Answer

The new computer software used in science classes represents a history threat to internal validity, as it is an external event that occurred during the study and could have influenced the students' math performance improvement.

Question 13

In clinical trials involving tests of new medical treatments it may be extremely difficult to get patients to agree to be randomly assigned to either the treatment or the control group.In these situations researchers can use

Accepted Answer

Quasi-experimental designs are used when random assignment is not possible, allowing researchers to study effects in a more natural setting while still attempting to control for confounding variables.

Question 14

A researcher trains observers to complete checklists while observing children's behavior on the schoolyard during recess.Over the course of the study,observers become more reliable in their observations.Any effect of a treatment in this study might be confounded with an ____________ threat to internal validity.

Accepted Answer

The improvement in observer reliability over the course of the study is an example of instrumentation, where changes in the measuring instrument (in this case, the observers) may affect the results. Therefore, any effect of a treatment might be confounded with an instrumentation threat to internal validity.

Question 15

Random assignment to conditions is used in true experiments to control which of the following threats to internal validity?

Accepted Answer

Random assignment to conditions helps to control for selection bias by ensuring that participants are assigned to groups in a way that is not influenced by any pre-existing differences in their characteristics or traits. This reduces the likelihood that any observed differences between groups are due to selection bias rather than the experimental manipulation. The other options (testing, history, subject attrition) are not addressed by random assignment and require other controls or methods to address them.

Question 16

When events that occur during the course of a study have a different effect on one group of participants than on another,the possible threat to internal validity is

Accepted Answer

The answer of When events that occur during the course...

Question 17

A physician wants to test the effectiveness of a new allergy medication.The physician consults a researcher who regularly conducts clinical trials.The physician tells the researcher that she has a backlog of 100 patients she is treating effectively with the prevailing medication but who could potentially benefit even more from the new medication.The researcher recommends that the physician do a true experiment because of the availability of a(n)

Accepted Answer

The researcher recommends a waiting-list control group, which is a type of true experiment where participants on the waitlist serve as the control group until they receive the new medication. This allows for a comparison between the effectiveness of the prevailing medication and the new medication, which is the goal of the study. Excess-demand, quasi-treatment, and convenience control groups are not relevant to this particular scenario.

Question 18

A psychologist examines the effect of a new therapy by first assessing patients' symptoms using a pretest,then administering eight weeks of therapy,and then administering a posttest.Based on this research design,the psychologists will be able to

Accepted Answer

This design lacks a control group, so it cannot establish causality (A), and without a diverse sample or replication, it cannot generalize to other patients (B).

Question 19

When,from the outset of a study,differences exist between the kinds of individuals in one group of an experiment and those in another,there is a potential threat to internal validity called

Accepted Answer

The potential threat to internal validity in this scenario is selection. The reason is that if the individuals in one group are different from those in another group at the beginning of the study, it may be difficult to attribute any observed differences between the groups to the independent variable (the variable being manipulated in the study) rather than to pre-existing differences between the groups.

Question 20

Participants for a treatment group are chosen because they score very low on a pretest measure of performance.When their performance improves on the posttest,the researcher

Accepted Answer

When participants are selected based on extreme scores (in this case, low scores on pretest), there is a high likelihood of statistical regression to the mean. This means that their scores are likely to improve on the posttest simply due to chance, regardless of any treatment effects. Therefore, the researcher should consider the possibility of statistical regression as an alternative explanation for the improvement in posttest scores.

Quiz 10: Quasi-Experimental Designs and Program Evaluation