The number of on line Monday stock trades at OHaganStockTrades com a subsidiary of oHaganBooks com was measured for 50 Mondays in a row with the following results Stock trades 0 99 100 199 200 299 300 399 400 499 Number of Mondays 6 12 14 10 8 Thus for example there were between 300 and 399 trades on 10 of the 50 Mondays The measurement classes are the ranges 0 99 100 299 etc We would like X to measure the number of stock trades on a randomly selected Monday and then calculate its probability distribution Since we only have information for ranges of values we replace each measurement class by its rounded midpoint Let us take them one by one The midpoint of the 0 99 range is 0 99 59 5 which we round to 50 2 100 199 The midpoint of the 100 199 range is 2 Now continue in the same way to obtain the remaining values of X QUIZ 149 5 which we round to 150 Stock trades 50 Number of Mondays 6 Now use the above frequency table to complete the estimated probability distribution of X 150 12 250 14 350 10 450 8