3727PsychologyMedium
A friend states that since he has been taking vitamin C, he has not had a single cold. His observation has little value in assessing the effects of vitamin C because:
Aof the effect of the observer on the observed
Bthere was no control group for comparison
Che has not calculated a correlation coefficient
Dhe does not specify his dosage of vitamin
Correct answer
B. there was no control group for comparison
Explanation
The correct answer is there was no control group for comparison.