Ivan wants to test how the amount of water consumed each day affects the number of facial blemishes people receive over a month. he gathers 12 people and divides them into 3 groups. he keeps everything the same for each group except for daily water and food intake. throughout the month, ivan tallies the number of facial blemishes each individual receives. the table details how ivan changed the independent variables for each group. note: group 1 is ivan's control group. what error did ivan make in the design of his inves