Answer:
(i) 41-45 mins
(ii) 40 mins
(iii) 75 workers
(iv) Rs10500
Explanation:
(i) The modal class is the class with the highest frequency.
Therefore, from inspection of the frequency table, the modal class is 41-45 mins since if has the highest frequency of 14.
(ii) As the data is grouped, to find an estimate of the mean, assume that every worker takes the value of the class mid-point. As the data is discrete, there are gaps between the classes, and so we also have to use lower and upper class boundaries to calculate the mid-points.
Class 21-25 : lower 20.5 | upper 25.5 | mid-point 23
Class 26-30 : lower 25.5 | upper 30.5 | mid-point 28
Class 31-35 : lower 30.5 | upper 35.5 | mid-point 33
Class 36-40 : lower 35.5 | upper 40.5 | mid-point 38
Class 41-45 : lower 40.5 | upper 45.5 | mid-point 43
Class 46-50 : lower 45.5 | upper 50.5 | mid-point 48
Class 51-55 : lower 50.5 | upper 55.5 | mid-point 53
Class 56-60 : lower 55.5 | upper 60.5 | mid-point 58
Mean = (sum of frequency x class mid-point) ÷ total frequency
⇒ Mean = (2 x 23 + 5 x 28 + 7 x 33 + 10 x 38 + 14 x 43 + 8 x 48 + 3 x 53 + 1 x 58) ÷ 50
⇒ Mean = 40 mins
(iii) 8 hours = 8 x 60 = 480 mins
Total time ÷ average time to make one doll = 480 ÷ 40 = 12
If the mean time to make a doll is 40 minutes, then one person can make 12 dolls in 8 hours.
Therefore, to calculate the number of workers required to make 900 dolls in 8 hours, divide the total number of dolls needed by 12:
900 ÷ 12 = 75
So 75 workers will be needed to make 900 dolls in 8 hours, given the mean time for a worker to make a doll is 40 mins.
(iv) Overtime is paid in excess of 6 hours. Therefore, each worker will be working 2 hours overtime.
Total amount of overtime pay = hours x rate x workers
= 2 x Rs70 x 75
= Rs10500