Controlling Confounds in a Posttest Only Nonequivalent Groups Design

A researcher wants to test a new fraction-teaching strategy. She implements it in one third-grade classroom and compares those students' final math scores to another classroom that used traditional methods. Students were not randomly assigned to these classrooms. What is the primary reason this design cannot establish that the teaching strategy caused any observed difference in scores?

In a study evaluating a new teaching strategy by comparing two existing third-grade classrooms, match each methodological term to the specific role it plays in this research example.

In a study comparing two pre-existing third-grade classrooms to test a new fraction-teaching strategy, the different disciplinary styles of the teachers are considered confounding variables that could independently explain the final math scores.

A researcher evaluates a new fraction-teaching strategy by comparing two existing third-grade classrooms in a posttest only nonequivalent groups design. Arrange the logical steps of the analytical process used to identify why this design fails to establish a causal relationship.

In the example of a study evaluating a new fraction-teaching strategy across two third-grade classrooms, which factor is explicitly mentioned as a preexisting confounding variable that could independently explain differences in math scores?

In the research example evaluating a new fraction-teaching strategy, arrange the procedural steps of the study in the correct chronological order.

A researcher claims that a new teaching strategy is effective based on a study comparing two pre-existing third-grade classrooms. In evaluating the internal validity of this claim, a psychologist would judge the evidence as weak primarily due to the absence of _____, as this failure prevents the researcher from ensuring the groups were equal before the intervention began.

A school administrator implements a new reading comprehension program in one existing fifth-grade classroom while another existing classroom continues with the traditional approach. Both classes take the same reading test at the end of the year. Because both classrooms are in the same school and follow the same curriculum guidelines, the administrator concludes that any score difference must be caused by the new reading program.

In the fraction-teaching posttest only nonequivalent groups study, analyze how each source of nonequivalence functions as a confound. Match each source to the specific mechanism by which it threatens the study's internal validity.

A researcher reports that third-grade students taught with the new fraction method scored significantly higher than students in the traditional classroom and concludes that the new method caused the improvement. A peer reviewer evaluating this study argues that this causal conclusion is not justified, primarily because the students were not _____ to the two classrooms.

In the context of evaluating a new fraction-teaching strategy, recall and describe the setup of a posttest only nonequivalent groups design. Specifically, identify the treatment and control groups, explain why the groups are considered nonequivalent, and list the three preexisting confounding variables described in the text that could independently explain any outcome differences.

Based on the case context, diagnose why the researcher cannot confidently conclude that the new teaching strategy caused the higher math scores. Explain how the lack of random assignment allowed specific preexisting factors to act as confounding variables, and clarify how these factors serve as alternative explanations for the outcome.

Imagine a school principal assigns students to classrooms based on behavior, placing students who need stronger discipline into one class and highly motivated students into another. If a researcher uses these pre-existing classes to test a new educational program without random assignment, apply the concept of confounding variables to explain in one to three sentences how this assignment method threatens the internal validity of the study.