Answer
$\approx \frac{n}{2}$
Work Step by Step
Average comparisons for a short sequential search in a sorted list: $\approx \frac{n}{2}$ (slightly less due to early stopping if the target is smaller than the last elements).
The exact expected number of comparisons formula for a list of size $n$ can be calculated with the formula:
Expected value = $\frac{Sum \space of \space all \space possible \space values}{Number \space of \space values}$
=> Expected value = $\frac{1+2+3+...+n}{n}=\frac{n(n+1)}{2n}=\frac{n+1}{2} $
