Overlap in Internal Validity Between Research Designs

Arrange the following research designs in order from LOWEST internal validity to HIGHEST internal validity.

A researcher wants to study whether a new therapy reduces anxiety. In Design A, participants are randomly assigned to either the therapy group or a no-therapy control group. In Design B, participants self-select into whichever group they prefer. Which design has higher internal validity, and what is the primary reason?

Based on the spectrum of internal validity, match each research scenario with the level of internal validity it typically provides.

True or False: According to the spectrum of internal validity, the structural feature that distinguishes a true experiment from a quasi-experiment—thereby placing it at the highest level of validity—is the manipulation of an independent variable.

In the comparison of internal validity across research designs, what is the primary structural reason that quasi-experimental research occupies the middle ground between experimental and non-experimental research?

Quasi-experimental research and non-experimental (correlational) research share the same level of internal validity because both lack the random assignment of participants.

A researcher evaluating the rigor of a causal claim finds that a study utilizes strict control over extraneous variables, the manipulation of an independent variable, and random assignment of participants. Consequently, the researcher would judge this design as possessing the _____ level of internal validity on the standard research spectrum.

Match each structural feature to the role it plays in determining where a research design falls on the internal validity spectrum.

A researcher compares a quasi-experimental study and a true experiment that both investigated the same causal relationship. The quasi-experimental study produced a weaker causal conclusion. Analyzing the structural source of this difference, the researcher determines that the quasi-experimental study lacked _____, which allowed pre-existing differences between groups to serve as alternative explanations for the observed outcomes.

A researcher wants to determine whether a new stress-management workshop causes a reduction in student anxiety. Evaluate each design approach below and arrange them in order from the approach that LEAST effectively supports a causal conclusion (order 1) to the approach that MOST effectively supports a causal conclusion (order 3), justifying your ranking based on the internal validity each design provides.