Define a random sample and use shifted totals

A production manager wants a random quality-control sample of one type of chocolate bar from the thousands produced at a factory in one day. For 70 sampled bars, mass $x$ grams satisfies $\sum(x-95)=287$ and $\sum(x-95)^2=1928$.

(i) State what random sampling means in this context.1 mark

(ii) Calculate unbiased population mean and variance estimates.2 marks