Research methods in psychology

1. We have seen repeatedly that experiments and non-experiments differ by the feature of manipulation (i.e., inclusion of a true independent variable).  

Fill in the blank below with a description that explains “quasi-experiment” and
how it is different from experimental and non-experimental designs.

Quasi-experiments are ________________________________________________.  

In addition, provide 3 specific research questions that could only be answered using a quasi-experimental design.  

2. Compared to experiments with control features, quasi-experiments have lower ____________ validity because _________________________________________________. Sometimes however, quasi-experiments have higher ________ validity because _______________. 

For each numbered design below, describe it and provide your own example of it.

Name of Design

Description/Features

Example

One-Group
Posttest Only

One-Group
Pretest-Posttest

Nonequivalent Posttest Only

Nonequivalent Pretest-Posttest

Interrupted Time Series (with Nonequivalent Groups)

Pretest-Posttest Design with Switching Replication

Switching Replication with Treatment Removal

In the section about one-group pretest-posttest design, your book discusses some threats to internal validity that can be controlled by counterbalancing conditions in within-subjects designs (discussed in chapter 5).  They are mentioned here because these threats to internal validity are present in quasi-experiments that lack the control features. Please give your own examples, not examples from the book.  

Name of Threat
to Internal Validity

Description

Example

History

Maturation

Testing

(usually includes practice and fatigue effects you have read about before)

Instrumentation