A control group was not used. The same type of pot and soil was used. Each plant received the same amount of water. Too much data will be collected in three weeks.
I gave my students this multiple choice question: Which statement is a MAJOR mistake in the experimental design?

Only one answer is correct among these 4 choices:
- A control group was not used.
- The same type of pot and soil was used.
- Each plant received the same amount of water.
- Too much data will be collected in three weeks.

Could you tell me which one is correct?

A control group was not used.