Answer :
Answer:
B
Step-by-step explanation:
B) because after each group is finished reading at a certain time, you'r going to test or see how their comprehension was affected by the amount of time read.
The situation that is an example of an observational study is " Having customers fill out a questionnaire about their favourite brand of toothpaste".
What is an observational study?
When researchers monitor the effect of a risk factor, diagnostic test, therapy, or other intervention without attempting to influence who is or is not exposed to it in observational studies.
For example: Consider someone standing on a popular street in a New York neighbourhood asking passers-by how many dogs they have, then analyzing the data to see if more pet food businesses are needed in the area.
As we know that in an observational study, the sample whose test/survey is been taken is completely random.
Therefore, the situation that is an example of an observational study is " Having customers fill out a questionnaire about their favourite brand of toothpaste".
Learn more about Observational Study:
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