The weights (in kilograms) of parcels handled in a courier office on a particular day were grouped as follows:
Weight (kg) 40 – 50 50 – 65 65 – 75 75 – 90 90 – 110
Frequency 5 12 20 8 5
Answer the following questions.
(i) Find the mean weight of the parcels.
(ii) Calculate the variance and the standard deviation of the parcel weights, correct to two decimal places.