Answer :
In studies with a group of individuals being tested in a series of treatment conditions, factors such as history, instrumentation, and maturation threaten called "internal validity'.
What does internal validity means?
The degree of confidence you have in the inexplicably of a cause-and-effect link found in a study is known as internal validity.
The types of internal validity are-
- Descriptive,
- experimental,
- quasi-experimental, and
- relationship-based
The internal validity is obtained by following ways-
- manipulation,
- elimination,
- inclusion,
- statistical control,
- randomisation.
To know more about the maturation, here
https://brainly.com/question/14661963
#SPJ4