Question

why aren't descriptive investigation repeatable

Answer 1

from this definition:

"Descriptive Investigation:
Involve describing and/or quantifying parts of a natural system. Example –
observing cells under a microscope and diagramming what is seen.
- Has a research question, procedures, and conclusion
- Used when little is known about the topic
- No hypothesis or prediction"

Since nothing is really being tested, it's essentially a method of gathering information that would help shed light on a proposed question. Unlike an experiment, which can be repeated to see if the results help support/don't support a conclusion, repeating a descriptive investigation will yield no more useful information

source for definition: http://mrcloudsclass.com/attachments/article/9/3%20Types%20of%20Investigations.pdf