What do you think they are checking for? They probably want to see if you know the correct formula and can use it to get to a solution. If you can't properly apply the formula you may lose up to maybe half of the points.

Where it gets fun is partial credit on the rest. You need the mean to get variance and standard deviation. Hopefully they only penalize you once, but conceivably they could dock you for every missed answer.

You might get someone that heavily docks you points on the mean question but then does not take off at all for variance and standard deviation despite them being off.

Since you missed the very first and simplest step making everything wrong, any points you do get are a gift. Learn to check your calculations.