Stage 9 - Q10 - 7 marks
20236
Times in minutes are grouped as \(0\le t<10\), \(10\le t<20\), \(20\le t<30\) with frequencies 2,3,5. Find the midpoint mean estimate and the tight interval guaranteed to contain the true mean. Can the estimate be above or below the true mean?
Hint
Replace every hidden value by its class lower bound, then by its upper bound, to bound the total.