MATURATION: physiological processes occurring within the participants that could account for any changes in their behavior

REGRESSION TO THE MEAN:the tendency that participants who receive extreme scores when tested, tend to have less extreme scores on subsequent retesting even in the absence of any treatment effects.

SELECTION OF SUBJECTS: Any bias in selecting and assigning participants to groups that results in systematic differences between the participants in each group.

MORTALITY: Differential dropping out of some subjects from the comparison groups before the experiment is finished, resulting in differences between the groups that may be unrelated to the treatment effects.

INSTRUMENTATION:Changes in the measurement procedures may result in differences between the comparison groups that are confused with the treatment effects.

TESTING:When participants are repeatedly tested, changes in test scores may be more due to practice or knowledge about the test procedure gained from earlier experiences rather than any treatment effects

HISTORY:Extraneous events occurring during the course of the experiment that may affect the participants' responses on the dependent measure.

INTERACTION:SELECTION BY MATURATION, INSTRUMENTATION, or HISTORY: The treatment and no-treatment groups, although similar at one point, would have grown apart (developed differently) even if no treatment had been administered.

DIFFUSION (or imitation of treatment):Threat to internal validity that can occur if participants in one treatment group become familiar with the treatment of another group and copy that treatment.

Spot the Internal Validity Threat that is MOST likely at work for each of the following scenarios:

1.The study ran for several weeks during the semester. About a week after it started, the university announced that they would be holding training sessions for faculty and staff about how to handle situations involving a gunman on campus. This shut down the study for several days as the university needed the lab building for training. The study then resumed according to script after the training. The researchers found that those in the experimental group did not differ in their memories regarding the presence of a gun compared to those in the control condition. That is, the mean score that a gun was present was similar for the experimental group (M = 65%, SD = 11.4%) and the control group (M = 63%, SD = 13.26%).

a.Maturation

b.Regression to the mean

c.Selection

d.Mortality

e.Instrumentation

f.Testing

g.History

h.Interactions

i.Diffusion

j.No Threat

2.The experiment proceeded as normal, with the experimental group hearing about the potential presence of a gun as the confederates left the study and the control group not hearing about the gun. All participants returned on day two for the interview with the police detective. After debriefing, none of the participants said they were aware that the theft was staged. The researchers found that those in the experimental group did incorporate the gun misinformation into their memories of the theft more than those in the control condition.That is, the mean score that a gun was present was much higher for the experimental group (M = 67%, SD = 12.4%) than the control group (M = 33%, SD = 11.16%).

a.Maturation

b.Regression to the mean

c.Selection

d.Mortality

e.Instrumentation

f.Testing

g.History

h.Interactions

i.Diffusion

j.No Threat

3.After viewing the theft and speaking with the experimenter as well as campus security, all participants were asked to return on day two to discuss what they saw more formally with the police detective. Unfortunately, a hurricane hit the next day and closed down campus for two weeks, so participants were unable to return as quickly as the researchers would have liked. Still, the interviews commenced three weeks after the theft, and researchers found that those in the experimental group did not differ in their memories regarding the presence of a gun compared to those in the control condition. That is, the mean score that a gun was present was similar for the experimental group (M = 65%, SD = 11.4%) and the control group (M = 63%, SD = 13.26%).

a.Maturation

b.Regression to the mean

c.Selection

d.Mortality

e.Instrumentation

f.Testing

g.History

h.Interactions

i.Diffusion

j.No Threat

4.To see how participants responded to questions about the presence of a gun immediately after the theft (on day one), campus security asked the participant how likely it was that the thief had a gun immediately after the incident. The experiment then proceeded as usual, with participants in either the experimental or control group. The next day (day two), the police detective also asked about whether the participant saw a gun. Data analysis showed that participants' answers about the likelihood that the thief had a gun became more extreme on follow-up questioning by the police detective. That is, regardless of whether they were in the control or experimental condition, participants who reported that the thief had a gun on day one were convinced he had a gun on day two. That is, the mean score that a gun was present was similar for the experimental group (M = 65%, SD = 11.4%) and the control group (M = 63%, SD = 13.26%).

a.Maturation

b.Regression to the mean

c.Selection

d.Mortality

e.Instrumentation

f.Testing

g.History

h.Interactions

i.Diffusion

j.No Threat

5.Thinking that hearing about a gun might be more emotionally stressful for females then males, the researchers made sure that all female participants were in the control condition while males heard the conversation about the presence of a gun. The researchers found that those in the experimental group did incorporate the gun misinformation into their memories of the theft more than those in the control condition. That is, the mean score that a gun was present was much higher for the experimental groups (M = 67%, SD = 12.4%) than the control group (M = 33%, SD = 11.16%).

a.Maturation

b.Regression to the mean

c.Selection

d.Mortality

e.Instrumentation

f.Testing

g.History

h.Interactions

i.Diffusion

j.No Threat

6.The researchers decided to collect all of the data from the control group early in the semester and then collect data from the experimental group later. Although the researcher scripted out exactly how the confederates were supposed to act for both conditions and what they were supposed to say, the confederates were still shy and nervous early in the semester. Fortunately, they grew much more confident in their performance as the semester progressed. The researchers found that those in the experimental group did incorporate the gun misinformation into their memories of the theft more than those in the control condition. That is, the mean score that a gun was present was much higher for the experimental group (M = 67%, SD = 12.4%) than the control group (M = 33%, SD = 11.16%).

a.Maturation

b.Regression to the mean

c.Selection

d.Mortality

e.Instrumentation

f.Testing

g.History

h.Interactions

i.Diffusion

j.No Threat

7.Thinking that hearing about a gun might be more emotionally stressful for females then males, the researchers made sure that all female participants were in the control condition while males heard the conversation about the presence of a gun. After viewing the theft and speaking with the experimenter as well as campus security, all participants were asked to return on day two to discuss what they saw more formally with the police detective. Unfortunately, a hurricane hit the next day and closed down campus for two weeks, so participants were unable to return as quickly as the researchers would have liked. Still, the day two interviews commenced three weeks after the theft, and researchers found that those in the experimental group did not differ in their memories regarding the presence of a gun compared to those in the control condition. That is, the mean score that a gun was present was similar for the experimental group (M = 65%, SD = 11.4%) and the control group (M = 63%, SD = 13.26%).

a.Maturation

b.Regression to the mean

c.Selection

d.Mortality

e.Instrumentation

f.Testing

g.History

h.Interactions

i.Diffusion

j.No Threat

8.To see just how participants responded to questions about the presence of a gun, campus security asked the participant how likely it was that the thief had a gun on day one. The police detective was similarly supposed to ask about whether the participant saw a gun, but the detective only had time to talk with half of the participants on day two. To choose which participants to ask back for this second interview, the researchers looked only at those who were really confident that they saw a gun on day one (they answered 75% likelihood or higher). The researchers found that those in the experimental group did not differ from those in the control group about the likelihood of a gun. That is, the mean score that a gun was present was similar for the experimental group (M = 67%, SD = 12.4%) and the control group (M = 63%, SD = 11.16%), though both were ironically less sure about the presence of a gun than they were the prior day.

a.Maturation

b.Regression to the mean

c.Selection

d.Mortality

e.Instrumentation

f.Testing

g.History

h.Interactions

i.Diffusion

j.No Threat

9.The experiment proceeded as normal, with the experimental group hearing about the potential presence of a gun as the confederates left the study and the control group not hearing about the gun. Unfortunately, hearing about the possible presence of a gun frightened some of the experimental participants, who did not show up for the second interview with the interviewer on day two. All of the control participants returned for the second interview. The researchers found that those in the experimental group did not differ from those in the control group about the likelihood of a gun. That is, the mean score that a gun was present during the second interview was similar for the experimental group (M = 67%, SD = 12.4%) and the control group (M = 63%, SD = 11.16%).

a.Maturation

b.Regression to the mean

c.Selection

d.Mortality

e.Instrumentation

f.Testing

g.History

h.Interactions

i.Diffusion

j.No Threat

10.The experiment proceeded as normal, with the experimental group hearing about the potential presence of a gun as the confederates left the study and the control group not hearing about the gun. Unfortunately, word spread around campus about a man with a gun who stole a laptop during a study. Unknown to the study researchers, many potential participants participated in the research anyway, and kept an eye out for a gun, knowing that they might be asked about it. The researchers found that those in the experimental group did not differ from those in the control group about the likelihood of a gun. That is, the mean score that a gun was present during the second interview was similar for the experimental group (M = 67%, SD = 12.4%) and the control group (M = 63%, SD = 11.16%).

a.Maturation

b.Regression to the mean

c.Selection

d.Mortality

e.Instrumentation

f.Testing

g.History

h.Interactions

i.Diffusion

j.No Threat