Ch. 11 – PSY 350

Which of the following is NOT one of the three most common threats to internal validity?

Emma is planning an experiment to examine whether reading to children increases their vocabulary size. She plans to measure the vocabulary size of a group of 18-month-olds, read to them three times a week for three months, then measure their vocabulary size again. How could Emma change the design of the study to remove a major threat to internal validity?

A city in California has asked Professor Rodriguez to conduct an experiment on earthquake preparedness. Professor Rodriguez will assess the preparedness of a random sample of residents in the city and the city will mail out their annual brochure on earthquake safety. Then, two weeks later, he will again assess the preparedness of those residents. Right after the brochures are mailed, a large earthquake is reported in Japan. What threat to internal validity does this pose?

Which threat to internal validity occurs when there is a greater systematic loss of participants in one condition than the other condition?

As part of an experiment on the effects of behavior modeling, a set of raters are evaluating the prosocial behavior in a series of videotapes of a class of preschoolers. Initially, the raters were quite strict in their ratings, but after three hours of rating, their criteria had changed. What type of threat to internal validity has occurred?

Some internal validity threats can be addressed simply by including a comparison group, while other internal validity threats can occur even in studies with a comparison group. Which of the following threats to internal validity would be improved with the inclusion of a comparison group?

Dr. Harrison wants to test the effectiveness of the support group he runs for undergraduates who have drinking problems. He recruits a group of students who have been referred to the counseling center. He randomizes them to two groups — a treatment group and a control group. The treatment group attends 10 structured support group sessions at 8:00 a.m. on Fridays that are facilitated by Dr. Harrison. The control group attends 10 unstructured meetings at 3:00 p.m. on Wednesdays that are facilitated by members of the group. Several of the participants in the treatment group stop attending the group after just a couple of sessions. All of the control group members attend their group regularly. At the end of the 10 weeks of groups, Dr. Harrison measures drinking behavior of the people who are still attending the groups. He finds that the drinking behavior of people who attended all 10 of the structured group sessions is less than the drinking behavior of people who attended all 10 of the unstructured group sessions. What kind of threat to internal validity should Dr. Harrison be concerned about?

Which of the following is NOT a problem that may contribute to a null effect in a study?

The students in a 50-student Introductory Psychology class were randomly assigned to one of two review sessions, each being taught with a different technique. The next day, every student got all 10 of the test questions correct. What problem does Professor Zhao have in determining the better teaching technique for review sessions?

Which of the following does NOT contribute to within-groups variability?

Individual differences can contribute to too much within-group variability. Which of the following is NOT a possible solution to individual differences?

In an experiment on improving children’s handwriting, two different techniques of improving handwriting and a control condition are used. Using a pretest/posttest design, both groups who received the treatment showed more improvement than the control group. However, the two groups didn’t show any difference from each other. The researcher believes that there is a difference, but that the 5-point assessment scale of handwriting cannot detect it. What measurement problem is the researcher concerned with?

Jared is conducting an experiment with ESP (extrasensory perception) training. He begins with a pretest of his 40 participants and divides them into two groups based on their scores. The participants with the 10 lowest scores are given extensive training on how to detect the signals. The participants with the 30 highest scores are given no training. Both groups are retested and the average score of the participants with the training improved, while the average score of the participants without the training actually fell. What threat to internal validity should Jared consider?

Lucia is interested in studying discrimination in hiring. She designs an experiment in which the participant takes the role of an employer looking at job candidates for a specific position. Each participant is given two very similar resumés—one of a candidate with a female name and one of a candidate with a male name—and is then asked to rate the suitability of each candidate for a job. Lucia finds no difference in participants’ ratings of male and female candidates. What threat to internal validity should she be concerned about?

What two types of validity in an experiment can observer bias threaten?

Frances did a study to investigate the effect of concreteness on memory. She created a list of 12 items that are very concrete (such as pencil and table) and a list of 12 items that are very abstract (such as justice and freedom). Each item was viewed for one second, then participants recalled them in order. Ten participants were tested in each condition. The study showed null effects. Which is NOT a possible explanation?

Emma is planning an experiment to examine whether reading to children increases their vocabulary size. She plans to measure the vocabulary size of a group of 18-month-olds, read to them three times a week for three months, then measure their vocabulary size again. What threat to internal validity should she be most concerned about?

Dr. Robinson designs an intervention that is meant to reduce college students’ risky sexual decisions. She hypothesizes that shaming college students about their risky sexual decisions will improve their decision making. She recruits participants and randomizes them to two conditions—the intervention group and the control group. The sexual behavior of all participants is measured in an interview with Dr. Robinson. After the pretesting, participants who are randomized to the intervention group are scheduled for an individual shaming session with Dr. Robinson. The control group does not participate in the shaming session. One week after the intervention, both groups are interviewed with Dr. Robinson about their sexual behavior over the past week. She finds that the intervention group reported less risky sexual decisions during the posttest interview. How could Dr. Robinson improve the internal validity of her study?

Frances did a study to investigate the effect of concreteness on memory. She created a list of 12 items that are very concrete (such as pencil and table) and a list of 12 items that are very abstract (such as justice and freedom). Each item was viewed for one second, then participants recalled them in order. Ten participants were tested in each condition. The study showed null effects, and almost all of the participants remembered all of the words on both lists. What is a likely solution?

Frances did a study to investigate the effect of concreteness on memory. She created a list of 12 items that are very concrete (such as pencil and table) and a list of 12 items that are very abstract (such as justice and freedom). Each item was viewed for one second, then participants recalled them in order. Ten participants were tested in each condition. The study showed null effects, and large variability within the groups. What is a likely solution?

On the first exam in an Introductory Psychology class, the grades are lower than Professor Mutola expected. She suspects that multitasking is to blame. She bans computers and cell phones from her class between the first and the second exam. When she compares the scores on the two exams, she finds a significant improvement on the second exam. What is the formal name for this type of design?

On the first exam in an Introductory Psychology class, the grades are lower than Professor Mutola expected. She suspects that multitasking is to blame. She bans computers and cell phones from her class between the first and the second exam. When she compares the scores on the two exams, she finds a significant improvement on the second exam. Professor Mitchell points out that in her classes, students always do better on the second exam because they are more used to her tests. What threat to validity is she suggesting?

On the first exam in an Introductory Psychology class, the grades are lower than Professor Mutola expected. She suspects that multitasking is to blame. She bans computers and cell phones from her class between the first and the second exam. When she compares the scores on the two exams, she finds a significant improvement on the second exam. When Professor Mutola rechecks her data, she finds that the five students with the lowest scores on the first exam have dropped the class. What threat to internal validity is this?

On the first exam in an Introductory Psychology class, the grades are lower than Professor Mutola expected. She suspects that multitasking is to blame. She bans computers and cell phones from her class between the first and the second exam. When she compares the scores on the two exams, she finds a significant improvement on the second exam. Professor Mutola looks back over the second exam and begins to wonder if it was just an easier exam. What threat to internal validity is she considering?

An instructor hypothesizes that doing jumping jacks will improve his students’ quiz performance. On Monday, he has his class sit in their chairs for five minutes before completing a multiple-choice quiz on their reading assignment. On Wednesday, he has his class do two minutes of jumping jacks before completing the same quiz that they took on Monday. The students performed better on the quiz on Wednesday. What is a possible threat to internal validity in this study?

In a repeated-measures design or quasi-experiment, a threat to internal validity that occurs when a systematic type of participant drops out of a study before it ends.

An experimental design problem in which independent variable groups score almost the same on a dependent variable, such that all scores fall at the high end of their possible distribution.

A threat to internal validity that occurs when some cue leads participants to guess a study’s hypotheses or goals. Also called experimental demand.

A study that uses a treatment group and a placebo group and in which neither the research staff nor the participants know who is in which group.

A study in which neither the participants nor the researchers who evaluate them know who is in the treatment group and who is in the comparison group.

An experimental design problem in which independent variable groups score almost the same on a dependent variable, such that all scores fall at the low end of their possible distribution. See also ceiling effect.

A threat to internal validity that occurs when it is unclear whether a change in the treatment group is caused by the treatment or by a historical factor or event that affects everyone or almost everyone in the group

A threat to internal validity that occurs when a measuring instrument changes over time from having been used before. Also called instrument decay.

In an experiment, an extra dependent variable researchers can include to determine how well an experimental manipulation worked.

A study design in which the observers are unaware of the experimental conditions to which participants have been assigned. Also called blind design.

A threat to internal validity that occurs when an observed change in an experimental group could have emerged more or less spontaneously over time.

The degree to which the recorded measure for a participant on some variable differs from the true value of the variable for that participant. Measurement errors may be random, if over a sample they both inflate or deflate true scores, or they may be systematic, in which case they may result in biased measurement.

The unsystematic variability among the members of a group in an experiment. Also called error variance, unsystematic variance.

A finding that an independent variable did not make a difference in the dependent variable; there is no significant covariance between the two. Also called null result.

A bias that occurs when observers’ expectations influence their interpretation of the participants’ behaviors or the outcome of the study.

An experiment in which a researcher recruits one group of participants; measures them on a pretest; exposes them to a treatment, intervention, or change; and then measures them on a posttest.

A response or effect that occurs when people receiving an experimental treatment experience a change only because they believe they are receiving a valid treatment.

The likelihood that a study will show a statistically significant result when some effect is truly present in the population; the probability of not making a Type II error when the null hypothesis is false.

A threat to internal validity related to regression to the mean, a phenomenon in which any extreme finding is likely to be closer to its own typical, or mean, level the next time it is measured (with or without the experimental treatment or intervention).

A threat to internal validity in which members are likely to drop out of either the treatment group or the comparison group, not both.

A threat to internal validity in which a historical or seasonal event systematically affects only the subjects in the treatment group or only those in the comparison group, not both.

Unrelated events, sounds, or distractions in the external environment that create unsystematic variability within groups in an experiment.

In a repeated-measures experiment or quasi-experiment, a kind of order effect in which scores change over time just because participants have taken the test more than once; includes practice effects and fatigue effects.

Demand Characteristics -She should be concerned that the participants guessed the manipulation in the study and gave what they thought was the more socially acceptable answer

Floor Effects -Floor effects are a special case of weak manipulations and insensitive measures, not one of the three most common threats

Change the design to eliminate ceiling effects -If all of the participants are getting all of the items correct then Frances should make the task more difficult to eliminate the ceiling effect

Attrition -Attrition is not a threat if it occurs uniformly across both groups, but if it is systematic it becomes a threat

Attrition -In a study that only lasts a few minutes, attrition isn’t usually an issue. There was no mention of participant loss.

Instrumentation -The raters, who are the measuring instrument, are changing over time

One-Group, Pretest/Posttest -She is using the first exam as the pretest and the second as the posttest

History -The earthquake is an external or \”historical\” event that occurs to everyone in the study, therefore the effect of the brochure cannot be assessed

Ceiling Effect -Because all the scores are squeezed together at the high end, the effect of the independent variable couldn’t be measured

Regression -The group that was given training had an unusually bad performance on the pretest, so was likely to regress upward in performance on the posttest, even without training.

Instrumentation -Instrumentation threat occurs when the pretest and posttest are not sufficiently equivalent

Adding more participants -Adding more participants to a study reduces the impact of individual differences within groups and will increase the chance of finding differences between groups

Use a double-blind study -Double-blind studies can control for observer effects and demand characteristics, but this wouldn’t help with the contribution of individual differences to within-group variability

She could make it a masked design -While in this case it is not possible for the participants to be blind to their condition, it is possible to make the person assessing the dependent variable blind to group membership, which should make the students more likely to be honest

Attrition -The rise in scores on the second test may be due to the loss of these extreme scores, which is attrition

She could add a comparison group -Adding a comparison group would allow her to show that her intervention had an effect above and beyond the normal effects of maturation

the percentage correct (dependent variable is never manipulated)

number of objects

All participants in the 2 minutes condition are tested at 8 am those in the 5 minute condition are tested at noon and those in the 10 minute condition are tested at 4 pm

selection effect

Maturation

History

independent groups factoria

the movie shown

no effect f role, no effect of others present and an interacrion

a threat to internal validity that occurs when an observed change in an experimental group could have emerged more or less spontaneously over time

a threat to internal validity that occurs when it is unclear whether a change in the treatment group is caused by the treatment or by a historical factor or event that affects everyone or almost everyone in the group

a threat to internal validity related to regression to the mean, a phenomenon in which any extreme finding is likely to be closer to its own typical, or mean, level the next time it is measured

in a repeated measures design or quasi experiment, a threat to internal validity that occurs when a systematic type of participant drops out of a study before it ends

a threat to internal validity that occurs when a measuring instrument changes over time from having been used before

a threat to internal validity in which members are likely to drop out of either the treatment group or the comparison, not both

a threat to internal validity in which members are likely to drop out of either the treatment group or the comparison g group, not both

a bias that occurs when observers expectations influence their interpretation of the participants behaviors or the outcome of the study

a threat to internal validity that occurs when some cue leads participants to guess a study’s hypotheses or goals

a study in which neither the participants nor the researchers who evaluate them know who is in the treatment group and who is in the comparison group

a study design in which the observers are unaware of the experimental conditions to which participants have been assigned

a study that uses a treatment group and a placebo group and in which neither the research staff nor the participants know who is in which group

a finding that an independent variable did not make a difference in the dependent variable; there is no significant covariance between the two

an experimental design problem in which independent variable groups score almost the same on a dependent variable, such that all scores fall at the high end of their possible distribution

an experimental design problem in which independent variable group score almost the same on a dependent variable, such that all scores fall at the low end of their possible distribution.

in an experiment, an extra dependent variable researches can include to determine how well an experimental manipulation worked

the unsystematic variability among the members of a group in an experiment

the degree to which the recorded measure for a participant on some variable differs from the true value of the variable for that participant. measurement errors may be random, if over a sample they both inflate or deflate true scores, or they may be systematic in which case they may result in biased measurement

unrelated events or distractions in the external environment that create unsystematic variability within groups in an experiment

the likelihood that a study will show a statistically significant result when some effect is truly present in the population; the probability of not making a type 2 error

floor effects

She could add a comparison group

large sample size

internal validity and construct validity

testing threat