Login
Copyright

Internal Validity in Psychology: Threats, Definition & Examples

An error occurred trying to load this video.

Try refreshing the page, or contact customer support.

Coming up next: Regression To The Mean in Psychology: Definition & Example

You're on a roll. Keep up the good work!

Take Quiz Watch Next Lesson
 Replay
Your next lesson will play in 10 seconds
  • 0:05 Definition of Internal…
  • 1:06 Threats to Internal Validity
  • 4:23 Lesson Summary
Add to Add to Add to

Want to watch this again later?

Log in or sign up to add this lesson to a Custom Course.

Login or Sign up

Timeline
Autoplay
Autoplay
Create an account to start this course today
Try it free for 5 days!
Create An Account

Recommended Lessons and Courses for You

Lesson Transcript
Instructor: Alyssa Gilston
Internal validity is a scientific concept that addresses the relationship between two variables. It refers to the extent that a study can rule out or make unlikely alternate explanations of the results.

Definition of Internal Validity

The purpose of conducting research is to arrive at valid and reliable conclusions about a variety of topics. We look at both the interactions between variables and how one variable impacts another variable. The dependent variable is the item that we plan to measure and change, while the independent variable is the intervention that we manipulate and that causes the change. For example, if we wanted to see if a certain medication promoted weight loss, the drug would be the independent variable, and the dependent variable would be the amount of weight loss achieved.

Scientific research cannot conclude with absolute certainty that the independent variable caused the change in the dependent variable. Internal validity is a scientific concept that addresses the relationship between two variables. It refers to the extent that a study can rule out or make unlikely alternate explanations of the results. Influences other than the independent variable that might explain the results of a study are called threats to internal validity.

Threats to Internal Validity

There are several threats to internal validity that may exist in an experiment.

History

History is a threat to internal validity; it refers to any event other than the independent variable that occurred in or out of the experiment that may account for the results of the experiment. It refers to the effects of events common to subjects in their everyday lives. Events that occurred in the weather, in the news or in the subject's personal lives could alter their performance in an experiment. In our weight loss example, the subject's eating habits and activity level outside of the experiment could impact the amount of weight loss or gain.

Maturation

Changes over time could also result from processes within the subjects themselves. Maturation refers to those processes such as growing older, growing stronger and even growing tired and impatient. Maturation will only be a problem if the design of the experiment does not identify and separate these effects. It is very common to see both history and maturation together, although it is not required.

Attrition

Attrition refers to the loss of subjects over time. Some studies last days, weeks and even months, and not all subjects remain for the entire duration. When a subject quits, moves, drops out or is removed from the research, it is called attrition.

Testing

Testing refers to what happens to our test performance when we practice or take a test again. Familiarity with the test could influence the performance on the second testing. Changes in the final scores may be a result of repeated testing.

Instrumentation

Instrumentation simply refers to the actual changes in the measuring procedures or the measuring device, rather than any changes in the person over time. This is one of the key reasons that we use standardized and formal testing procedures when conducting any type of assessment.

Statistical Regression

Statistical regression refers to the tendency for extreme scores to revert or regress toward the mean (or average) of a distribution when a measure is readministered. For example, if an event occurs during the day just before or just after the hour, one could forecast that the event will next occur on the hour in the future.

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

Register for a free trial

Are you a student or a teacher?
I am a teacher

Unlock Your Education

See for yourself why 30 million people use Study.com

Become a Study.com member and start learning now.
Become a Member  Back

Earning College Credit

Did you know… We have over 95 college courses that prepare you to earn credit by exam that is accepted by over 2,000 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

Transferring credit to the school of your choice

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.

Create an account to start this course today
Try it free for 5 days!
Create An Account
Support