Back To Course

College Algebra: Help and Review27 chapters | 229 lessons | 1 flashcard set

Are you a student or a teacher?

Try Study.com, risk-free

As a member, you'll also get unlimited access to over 75,000 lessons in math, English, science, history, and more. Plus, get practice tests, quizzes, and personalized coaching to help you succeed.

Try it risk-freeWhat teachers are saying about Study.com

Already registered? Login here for access

Your next lesson will play in
10 seconds

Lesson Transcript

Instructor:
*Yolanda Williams*

Yolanda has taught college Psychology and Ethics, and has a doctorate of philosophy in counselor education and supervision.

Test-retest reliability coefficient is a measure of how consistent the results of a test are over time. Learn more about the test-retest reliability coefficient from examples, and test your knowledge with a quiz.

Suppose you are a child psychologist looking for a way to measure test anxiety in children. One of your colleagues suggests that you use the Children's Test Anxiety Scale (CTAS). You thank your colleague and purchase the test.

You find information that indicates that the CTAS is a **valid** measure. That is, that the CTAS is able to accurately measure the anxiety level of children. You begin to wonder if the results of the CTAS are consistent, or **reliable**. The CTAS would be considered reliable if it would produce the same results each time that we use it.

You do not find much information about the reliability, so you decide to measure the reliability on your own. There are four different types of reliability that you could examine:

- Inter-rater reliability: The degree to which raters are being consistent in their observations and scoring in instances where there is more than one person scoring the test results.
- Internal consistency: The degree to which all of the items on a test measure the same construct.
- Alternate forms reliability: In instances where there are two forms of a test that measure the same construct, the degree to which the results on the two tests are consistent.
**Test-retest reliability**: The degree to which the results are consistent over time.

**Test-retest reliability** is the most common measure of reliability. In order to measure the test-retest reliability, we have to give the same test to the same test respondents on two separate occasions. We can refer to the first time the test is given as T1 and the second time that the test is given as T2. The scores on the two occasions are then correlated. This correlation is known as the **test-retest-reliability coefficient**, or the **coefficient of stability**.

The closer each respondent's scores are on T1 and T2, the more reliable the test measure (and the higher the coefficient of stability will be). A coefficient of stability of 1 indicates that each respondent's scores are perfectly correlated. That is, each respondent score the exact same thing on T1 as they did on T2. A coefficient correlation of 0 indicates that the respondents' scores at T1 were completely unrelated to their scores at T2; therefore the test is not reliable.

So, how do we interpret the coefficients of stability that are between 1 and 0? The following guidelines can be used:

- 0.9 and greater: excellent reliability
- Between 0.9 and 0.8: good reliability
- Between 0.8 and 0.7: acceptable reliability
- Between 0.7 and 0.6: questionable reliability
- Between 0.6 and 0.5: poor reliability
- Less than 0.5: unacceptable reliability

When we use test-retest reliability, we are making the assumption that there is not a significant change in the construct that we are measuring between the first and second times that we measure it. If we give the same measure twice, the correlation between T1 and T2 is affected by the amount of time that passes between the two. The less time between T1 and T2, the higher the correlation; conversely, the larger the time gap between T1 and T2, the lower the correlation. This is due to the fact that the closer the time gap, the more similar the contributing factors to error.

Suppose that you took a group of 104 children and had them each complete the CTAS. One month later, you have them complete the CTAS again. You correlate their scores and get a coefficient of stability of 0.92. Your findings indicate that the CTAS has excellent test-retest reliability. Therefore, the CTAS results are consistent over time.

Suppose that a group of high school seniors took the Wechsler Adult Intelligence Scales (WAIS) at the end of the first semester of their senior year. Six months later, the same students took the WAIS again. The scores were correlated, yielding a coefficient of stability of 0.7. This is an acceptable reliability coefficient.

Upon further analysis, you notice that T2 scores were higher than T1 scores. Given that the students were provided with additional knowledge and gained new skills in those six months between T1 and T2, you would expect a slight increase in scores on the WAIS.

Test-retest reliability is one of four types of reliability. Test-retest reliability refers to the degree to which test results are consistent over time. In order to measure test-retest reliability, we must first give the same test to the same individuals on two occasions and correlate the scores. The resulting correlation is the coefficient of stability - the more similar the scores, the higher the correlation. The test-retest reliability is heavily dependent upon the amount of time that passes between the two occasions. So, now you know all about test-retest reliability. And remember, just because test results are reliable, it does not mean that they are valid; but a valid test is always reliable!

The information you glean from this lesson can be drawn upon when you attempt to:

- List the four types of reliability
- Interpret test-retest reliability
- Indicate the effects of time on test-retest reliability
- Cite pertinent examples

To unlock this lesson you must be a Study.com Member.

Create your account

Are you a student or a teacher?

Already a member? Log In

BackWhat teachers are saying about Study.com

Already registered? Login here for access

Did you know… We have over 160 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Not sure what college you want to attend yet? Study.com has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

You are viewing lesson
Lesson
12 in chapter 25 of the course:

Back To Course

College Algebra: Help and Review27 chapters | 229 lessons | 1 flashcard set

- Go to Fractions

- Go to Factoring

- Probability of Independent and Dependent Events 12:06
- How to Calculate Mean, Median, Mode & Range 8:30
- Organizing and Understanding Data with Tables & Schedules 6:33
- Understanding Bar Graphs and Pie Charts 9:36
- Reading and Interpreting Line Graphs 6:09
- Creating & Interpreting Scatterplots: Process & Examples 6:14
- What is a Histogram in Math? - Definition & Examples 5:12
- Using Tables and Graphs in the Real World 5:50
- Math Combinations: Formula and Example Problems 7:14
- How to Calculate a Permutation 6:58
- Probability of Compound Events: Definition & Examples 5:40
- Test-Retest Reliability Coefficient: Examples & Concept 5:15
- Go to Data, Statistics & Probability

- Computer Science 109: Introduction to Programming
- Introduction to HTML & CSS
- Introduction to JavaScript
- Computer Science 332: Cybersecurity Policies and Management
- Introduction to SQL
- Progressive Politics & American Imperialism
- Reconstruction, Westward Expansion, Industrialization & Urbanization
- North America & the 13 Colonies
- The Renaissance & The Age of Exploration
- Algorithmic Analysis, Sorting & Searching
- CEOE Test Cost
- PHR Exam Registration Information
- Claiming a Tax Deduction for Your Study.com Teacher Edition
- What is the PHR Exam?
- Anti-Bullying Survey Finds Teachers Lack the Support They Need
- What is the ASCP Exam?
- ASCPI vs ASCP

- Convergent Sequence: Definition, Formula & Examples
- Mauryan Empire Art & Culture
- Multi-Dimensional Arrays in C Programming: Definition & Example
- Tests for Identifying Common Gases
- Singing Lesson Plan
- Arrays & Strings in JavaScript: Conversion & String Methods
- Heuristic Methods in AI: Definition, Uses & Examples
- Quiz & Worksheet - Average & Instantaneous Rates of Change
- Quiz & Worksheet - Speed, Velocity & Acceleration
- Quiz & Worksheet - Functions & Parameters Overview
- Quiz & Worksheet - Incremental & Radical Change
- Flashcards - Measurement & Experimental Design
- Flashcards - Stars & Celestial Bodies
- 7th Grade Math Worksheets & Printables
- Lesson Plan Templates

- AP Music Theory Syllabus Resource & Lesson Plans
- Organizational Behavior Management
- Basic Geometry: Help & Review
- UExcel Foundations of Gerontology: Study Guide & Test Prep
- Common Core ELA Grade 7 - Speaking & Listening: Standards
- Algebra II - Conic Sections: Tutoring Solution
- 9th Grade Literary Terms: Help and Review
- Quiz & Worksheet - Planaria Digestive System
- Quiz & Worksheet - Ecological Succession Types & Stages
- Quiz & Worksheet - The Pricing Framework in Marketing
- Quiz & Worksheet - Developing a Main Idea, Thesis Statement & Topic Sentences
- Quiz & Worksheet - Electron Configurations in Atomic Energy Levels

- Pricing Strategy and Consumer Perception
- Ethnic Groups in Egypt
- New Mexico State Standards for Science
- ACT Accommodations for ELL Students
- Massachusetts Science Standards
- 504 Plans in Massachusetts
- WV Next Generation Standards for Science
- South Dakota State Standards for Social Studies
- Next Generation Science Standards for Kindergarten
- ADHD Advocacy Groups
- Multiplication Math Games
- What is the EPT Test?

- Tech and Engineering - Videos
- Tech and Engineering - Quizzes
- Tech and Engineering - Questions & Answers

Browse by subject