Calculate the quartile deviation and its coefficient from the following data:

Age in Years:	20	30	40	50	60	70	80
No. of members:	13	61	47	15	10	18	36

Compute mean deviation about median from the following data:

x	f
58	15
59	20
60	32
61	35
62	35
63	22
64	20
65	10
66	8

Find out the coefficient of mean deviation about median in the following series

Age in years	0-10	10-20	20-30	30-40	40-50	50-60	60-70	70-80
No. of persons	8	12	16	20	37	25	19	13

Bag I contains 3 Red and 4 Black balls while another Bag II contains 5 Red and 6 Black balls. One ball is drawn at random from one of the bags and it is found to be red. Find the probability that it was drawn from Bag I.

Three boxes B₁, B₂, B₃ contain lamp bulbs some of which are defective. The defective proportions in box B₁, box B₂ and box B₃ are respectively \(\frac { 1 }{ 2 } ,\frac { 1 }{ 8 } \ and \ \frac { 3 }{ 4 } \). A box is selected at random and a bulb drawn from it. If the selected bulb is found to be defective, what is the probability that box B₁ was selected?