As discussed before, the 1st question states more bias, while the 2nd is more neutral on a personal basis.
Answer: Reading further, surveys are not typically known to have control groups since they are based on opinion. If they're studying the psychology of the question then the 2nd group would be the control as stated before.
If just wondering the general opinion of the data, then both of these two groups could be considered as controls for understanding the preferences for shower time. And also the mean between both groups of data could possibly be used as another control variable.
Taking the common definition for control groups as something used to benchmark a test sample, it's still most likely do you prefer to take a shower in the morning, afternoon or night being the control group to benchmark the first group that is questioned.
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