Cristina came up with \( [-2.35,-2.05] \) for the mean difference between the number of hours per week students spend doing homework for their English class and their math class. The midpoint of this interval is the sample mean difference. It is calculated as: \( \frac{-2.35-2.05}{2} \) Calculate this midpoint.

It looks like there's a small mistake in Cristina's formula for finding the midpoint. The correct formula to find the midpoint between two numbers \( a \) and \( b \) is \( \frac{a + b}{2} \). Here, we should be adding the two endpoints of the interval: \[ \frac{-2.35 + (-2.05)}{2} = \frac{-2.35 - 2.05}{2} = \frac{-4.40}{2} = -2.20 \] So, the midpoint, or the sample mean difference in this case, is \(-2.20\) hours.