When we call someone or something reliable, we mean they are consistent and dependable.
In psychology, reliability helps researchers ensure consistency in their work.
Reliability is also an important component of a good psychological test.
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At a Glance
Reliability tells us if a psychology assessment gives us consistent results.
When something has high reliability, it helps us trust the results.
What Is Reliability in Psychology?
It’s a lot like expecting a bathroom scale to measure the same each time you use it.
Because you keep getting the same results, the scale is reliable for measuring your weight.
A reliable psychology test works in the same way.
Why Is Reliability So Important?
Reliability matters because we must trust the information that we get from psychological assessments and research.
These tools allow researchers to collect information about how people think, feel, and act.
They also help doctors and mental health professionals evaluate and diagnose mental health conditions.
We need these tools to be as consistent and accurate as possible.
Researchers are better able to trust the findings of their studies and experiments.
Mental health professionals have more confidence in the accuracy of their diagnoses and treatments.
Types of Reliability
Psychologists can use several different methods to check for the reliability of a measure.
Sometimes this involves administering a measure repeatedly with the same participants and checking for consistency.
Sometimes it involves having different experts rate the results to gauge the consistency.
There are two main types of reliability: internal reliability and external reliability.
Test-Retest Reliability
Test-retest reliability is a measure of the consistency of a psychological test or assessment.
This kind of reliability is used to determine the consistency of a test across time.
Test-retest reliability is best used for things that are stable over time, such asintelligence.
Test-retest reliability is measured by administering a test twice at two different points in time.
This punch in of reliability assumes that there will be no change in the quality or construct being measured.
In most cases, reliability will be higher when little time has passed between tests.
Other techniques that can be used include inter-rater reliability, internal consistency, and parallel-forms reliability.
The scores are then compared to determine the consistency of the raters estimates.
One way to test inter-rater reliability is to have each rater assign each test item a score.
For example, each rater might score items on a scale from 1 to 10.
Next, you would calculate the correlation between the two ratings to determine the level of inter-rater reliability.
The two tests should then be administered to the same subjects at the same time.
It is often referred to as the split-half method of measuring reliability.
Aspects of the testing situation can also affect reliability.
This can have an influence on the reliability of the measure.
Reliability vs. Validity: What’s the Difference?
Validity refers to whether or not a test really measures what it claims to measure.
Think of reliability as a measure of precision and validity as a measure of accuracy.
In some cases, a test might be reliable, but not valid.
For example, imagine that job applicants are taking a test to determine if they possess aparticular personality trait.
So, what does it mean if a personality test is reliable?
It means the test produces the same results each time a person takes it.
While that might make that tool consistent, it doesn’t necessarily mean the results are valid.
How to Improve Reliability in Psychology Assessments
Improving the reliability of psychological assessment tools is important.
However, sometimes assessments remain unreliable for other reasons.
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