What was the nickname given to the middle ages?

Dark ages or the Renaissance

Explanation:

Things belonging to this period are described as medieval. The early part of this period is sometimes called the Dark Ages and the period after it is the Renaissance.

The question says,'validity that involves how well a study is designed and administered is validity. The correct option is A. internal validity refers to how well a research project was conducted. The objective of most projects is to show that one variable causes a change in another variable, therefore it is part of internal validity to ensure that more than one independent variable do not act at the same time.