Question

For each scenario, identify the threat to internal validity (MRS SMITH), explain why that scenario consists of that threat, then brainstorm a way to avoid that threat to internal validity. Hint: Each threat is only shown below once.

BACKGROUND INFORMATION
Research has shown that child abduction is a major problem in our society, the vast majority of young children are susceptible, and that abductions may be prevented by teaching children to resist enticements. The goal in this study was to teach children, upon being enticed by stranger, to say "No, I have to go ask my teacher" and then to quickly run away. The experimenter wanted to evaluate the effectiveness of a 20-minute interactive videotape program that was specially designed to teach children these behaviors in a school setting. She selected for subjects students in first grade classes at an elementary school, all of whom participated with parental consent.
In the Experimental condition, children viewed the interactive video; in the Control condition, children viewed a cartoon of equal duration having nothing to do with child abduction.
A Generalization Probe tested what each child would do in a potential abduction situation. While the children were silently working on their math homework, a new student teacher removed the children from class, individually, under the pretense of participating in sports. The student teacher pretended to forget something and left the child alone in the school yard. A stranger approached the child, made small talk, and then attempted to lure the child into his car by promising treats. When the stranger walked away (with or without child), the student teacher called out the child's name and the stranger moved quickly out of sight. The child was then returned to class. The roles of student teacher and stranger were played by graduate students of the experimenter.
For purposes of data analysis, a score of zero was given if a child went with the abductor, a score of one if the child stayed nearby with no refusal, a score of two if the child stayed nearby but verbally refused, a score of three if the child ran away with no refusal, and a score of four if the child ran away and verbally refused.
SCENARIO 4
The name of each child in the classes was written on a separate slip of paper. All the slips were put in a bowl and mixed up thoroughly. Students were assigned to the Experimental Group and to the Control Group alternately as their names were pulled out of the bowl one at a time. One day at school, the children in the Control Group were told to go to one room and children in the Experimental Group to another room, where they were exposed to their respective conditions. Two days later, the Generalization Probe was conducted. For ease of record keeping, all Control Group children were tested first, then all the Experimental Group children. The student teacher scored children's responses to the confederate's lures. In the beginning, he hid indoors and strained to see and hear through an open window; later on, he discovered he could see and hear better by hiding outside and peeking around a corner. The mean score for children in the Control Group was 1.2 and the mean score for children in the Experimental Group was 3.4. We conclude that the 20-minute interactive video improved the children's self-protection skills in a potential abduction situation.
SCENARIO 5
One day at school, the children viewed the 20-minute cartoon (Control condition). Two days later, the Generalization Probe was conducted. Then, in a class the following week, the children viewed the 20-minute interactive video (Experimental condition). The plan was to administer a second Generalization Probe two days after that. However, at this point, the experimenter realized that she had insufficient funding to complete the study and would only be able to retest ten children. She selected the ten poorest performing children on the first Generalization Probe, the mean score of which was 0.1. Their mean score on the second Generalization Probe was 2.5. We conclude that the 20-minute interactive video improved the children's self-protection skills in a potential abduction situation.

Answer 1

Scenario 4: The threat to internal validity is Selection, as the random assignment process was compromised by alternately assigning students to the Experimental and Control Groups. To avoid this, random assignment should be maintained to ensure group equivalence.

Scenario 5: The threat to internal validity is Selection, as the experimenter selectively retested the poorest performing children. To avoid this, the retest should involve a randomly selected sample from both Experimental and Control Groups.

Step-by-step explanation:

In Scenario 4, the threat to internal validity is Selection. This is because the random assignment process, crucial for ensuring group equivalence, was compromised by alternately assigning students to the Experimental and Control Groups. This non-random assignment introduces the risk that the groups may differ systematically, impacting the study's internal validity. To address this, the experimenter should ensure strict adherence to random assignment, perhaps by using a computer-generated randomization process or a random number table.

In Scenario 5, the threat to internal validity is again Selection. The experimenter selectively retested the poorest performing children, introducing bias into the retest sample. This selective retesting may contribute to an overestimation of the effectiveness of the interactive video. To mitigate this threat, the experimenter should retest a randomly selected subset of participants from both the Experimental and Control Groups. This approach ensures that the retest sample is representative of the overall study population, enhancing the internal validity of the conclusions drawn from the study.