Reliability and Validity

Meaning of Reliability and Validity

At first glance, you may think these terms have very basic definitions; however, each of their meanings can be increasingly intricate and significant in terms of psychological research. Both concepts are fundamental to understand when learning about experiments and the scientific method.

Reliability

In terms of scientific investigation, the definition of reliability is the presence of a stable and constant outcome after repeated measurement (Jackson, 2014). To put it into perspective, think of any form of psychological research using tests to measure specific outcomes. A test that is considered reliable will show similar outcomes each time it is administered. This consistency and dependability add value to the tests being used in research.

Validity

Validity is the term used to describe the indication that a test or tool of measurement is true and accurate. In other words, a valid test or tool is measuring the exact unit that it states to measure. There are examples of validity in day-to-day life. Think of a driver's license and how it is only valid if all the information about the driver is true and accurate. In psychology research, a test can only be considered valid if the outcome is accurate to what the test claims to measure.

Fg. 1 Reliability and validity, commons.wikimedia.org

Issues with Reliability and Validity

Within the domain of psychological research methods, any errors in the reliability and validity of a test or experiment are very detrimental to the value of the research. Before any scientific article, journal, or experiment can be posted, the findings must first meet standards of both reliability and validity. Unfortunately, instances in which these standards are not met may lead to unethical research and false or misleading claims.

This is just one devastating example of what can happen once certain study standards are compromised. These significant moments in the history of scientific research put an emphasis on the importance of reliability and validity in the realm of scientific investigation.

Errors in Reliability

There are common errors made in psychological research methods that may impact the reliability of a study. These types of issues include:

Method Error

A method error can occur due to the experimenter's actions or the testing atmosphere.

Questions asked about method error include:

• Is the experimenter using the tool of measurement correctly? Is the tool functioning properly?

• Is the environment of the test affecting the outcome of the measurement?

Trait Error

In trait errors, issues of reliability stem from the actual subjects of the experiments.

Questions asked about trait error include:

• Is the subject using biased actions or answers?

• Are they feeling well?

  • A subject who is feeling unwell may not perform as they would usually, thus affecting the outcome and reliability of the study.

Errors in Validity

Similar to the issues within reliability, certain types of errors in research may also jeopardize the experiment's validity. A few of these errors are known:

Maturation

Maturation may affect the validity of an outcome of long studies. Could the passage of time interfere with the initial performance of the test? How might a participant or test be affected during this time allotted?

Biases

Biases that may occur in the selection of participants may negatively impact the validity of the study. When the selection of the participants happens under bias, the ability for the study's outcomes to be generalized amongst a population becomes disabled.

Interaction Effects

Interaction effects can impact the validity in cases where there are pretests or multiple tests involved in one study. The application of a pretest can interfere with another measurement or test that follows.

As you can see, many issues can influence the value and credibility of any scientific investigation or study. Analyzing the errors that may decrease the reliability and validity of research is one of the highest priorities in the scientific method.

Reliability and Validity in Research

The scientific method is applied in all facets of scientific research and investigation. This process employs rigorous empirical methods to get a reliable and valid outcome. There are several examples of reliability and validity in psychology research methods. Assessing these examples will help you better understand the type of reliability and validity for each situation in psychology research.

Examples of Reliability and Validity

There are four types of reliability in psychology research, all of which indicate levels of consistency in various situations. The three types of validity measure the truthfulness and accuracy of tests in many different ways.

Test/Retest Reliability

This type of reliability in research tests the consistency of results over time by administering the same test more than once.

Alternate-Forms Reliability

By using multiple forms of similar tests, a researcher can indicate whether the measurement is reliable depending on the consistency of an outcome. This is why the method is named alternate-forms.

Split-Half Reliability

This is when a study splits the test into two parts and measures the stability between measurement items in both test halves. While this does not account for the consistency over time, it does measure the reliability of the content within the test itself.

Interrater Reliability

This refers to measuring reliability by assessing the consistency of observations across raters/judges.

Content Validity

A test with content validity aims to measure the relevance across all content/ items within the given test, not just in one area.

Criterion Validity

The analysis of the accuracy of a test in predicting the abilities or outcomes of participants.

Construct Validity

One of the most important forms when measuring validity is construct validity. This is because it is one of the most utilized in psychology as it analyzes the extent to which a test measures the construct it claims to measure.

Within qualitative research methods, validity and reliability can be determined through the consistency and objectives of the data outcomes, participants, types of tests, and researcher observations.