Experimental Design in Psychology

Questions and Answers

What is an essential feature of a simple randomized participants design?

Participants receive no variation of the independent variable.

Participants are grouped by their pre-existing characteristics.

Participants are assigned based on convenience sampling.

Participants are randomly assigned to different groups for treatment. (correct)

In the context of a true experimental design, what is critical for establishing a cause-effect relationship?

Presence of a confounding variable.

Control of extraneous variables. (correct)

Manipulation of a dependent variable.

Use of non-random assignment.

Which statement best describes a non-equivalent control group design?

Control and experimental groups may differ due to non-random assignment. (correct)

All participants are treated equally without a control group.

Participants are randomly assigned, ensuring equivalent groups.

All variables except for the independent variable are manipulated.

What is a potential issue with confounding variables in experimental designs?

They can obscure the relationship between the independent and dependent variable. Signup and view all the answers

Which example illustrates an inappropriate use of a simple randomized design?

Assigning groups based on the participants' skill level. Signup and view all the answers

How does a quasi-experimental design differ from a true experimental design?

Quasi-experimental designs do not have random assignment to groups. Signup and view all the answers

What method involves including only participants with a specific amount or type of a confound variable?

Matching by holding confound variables constant Signup and view all the answers

Which control technique involves treating a confounding variable as an independent variable?

Matching by building the extraneous variable into the design Signup and view all the answers

When equating participants in an experiment, which variable is commonly controlled?

Gender or age Signup and view all the answers

Which design would likely be used if researchers want to compare effects in naturally occurring groups without random assignment?

Non-equivalent control group design Signup and view all the answers

Which of the following is a fundamental issue raised by confounding variables?

Misinterpretation of cause and effect Signup and view all the answers

In a study involving TV violence, how should children of different ages be grouped to control for age as a confounding variable?

By age and then randomly assigning them to groups Signup and view all the answers

What is a key characteristic of quasi experimental designs?

They are conducted after the groups have been formed. Signup and view all the answers

What is a major limitation of non-equivalent control group designs?

They lack random assignment, leading to potential selection differences. Signup and view all the answers

In non-equivalent pretest-posttest designs, what could account for differences observed between groups?

Initial differences between groups or the independent variable. Signup and view all the answers

How do quasi experiments generally differ from true experiments?

Quasi experiments do not have random assignment of subjects. Signup and view all the answers

What is a plausible reason for a quasi experiment to still be considered valid despite its limitations?

It offers insights even without control over confounding variables. Signup and view all the answers

What may occur if differences between groups in a quasi experiment are attributed solely to the independent variable?

The influence of confounding variables is ignored. Signup and view all the answers

Which of the following best exemplifies the non-equivalent control group design?

A test group receives a new medication while a similar group does not. Signup and view all the answers

Which factor primarily reduces the internal validity of a quasi experimental design?

The inability to manage confounding variables. Signup and view all the answers

Study Notes

Quasi Experiment Overview

Quasi experiments, also known as 'ex post facto' studies, are conducted after groups have already formed.
Internal validity may be compromised due to the inability to control confounding variables, but this does not invalidate the results.

Types of Quasi Experimental Designs

Two primary designs are recognized in quasi-experimental research:
- Non-equivalent control group design
- Non-equivalent pretest-posttest design

Non-Equivalent Control Group Design

Compares the performance between an experimental group and a non-equivalent control group, lacking random subject assignment.
The absence of randomization leads to potential confounding variables that can influence results.
Example: Evaluating the effect of stress management on hypertensive patients, where one group receives treatment while another does not.
Differences in group outcomes may arise either from the treatment effect or pre-existing discrepancies between the groups.

Non-Equivalent Pretest-Posttest Design

Involves pretesting both an experimental and a control group followed by posttesting, where groups are still non-equivalent.
Variations in outcomes can result from initial differences or the impact of the independent variable being tested.

Comparing Quasi Experiments with True Experiments

True experiments typically feature random assignment and control over independent variables, enhancing internal validity.
Quasi experiments provide valuable insights but often require cautious interpretation due to potential confounding variables.

Simple Randomized Participants Design

Utilizes random assignment of participants across various levels of an independent variable to establish causation.
Example: Testing the effect of color on taste perception using three experimental groups with different treatment levels and one control group.
Can analyze the influence of feedback types on performance by comparing several groups subjected to different feedback conditions.

Control Techniques in Experiments

Matching by holding confounding variables constant ensures participants share specific characteristics to minimize variability.
Extraneous variables can be incorporated into study design to control for their effects, treating them as additional independent variables.
Participant equating based on specific variables, such as age or gender, is vital to maintain balanced groups for accurate comparisons.

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Description

Explore the principles of experimental design including the concepts of independent and dependent variables. This quiz examines simple randomized designs and extends to between-participant designs with various levels of independent variables. Test your understanding of these fundamental concepts in psychology research.