Question

The distribution below shows the number of wickets taken by bowlers in one-day cricket matches. Find the mean number of wickets by choosing a suitable method. What does the mean signify?
Number of wickets 20 - 60 60 - 100 100 - 150 150 - 250 250 - 350 350 – 450
Number of bowlers 7 5 16 12 2 3

Answer 1

Here,

the class size varies , and the xi's are

large .

Let us still apply the step deviation method

with

a = 200 ,

h = 20

mean = 200 +[ ( -106 )/45 ]×20

= 200 - 47.11

= 152.89

The average number of wickets taken

by these 45 bowlers in one - day

cricket is 152.89

I hope this helps you.

: )

Answer 2

Answer:

Well answering it with the direct method would be tedious.

Plus, this is an example from NCERT written in an attempt to show that we can still apply the step-deviation method even when the class sizes (h) are unequal.

Let’s take a=200.

Why do we take it? Cos it’s somewhere in the middle of the class intervals. And also it’s a pretty simple yet large number to work with.

Now what about ‘h’?

Well, we could find suitable h after filling the rest of the table. By suitable I mean, which is a suitable divisor to all the di’s (deviation).

In the text book, h=20.

Notice that ‘a=200’ is a multiple of ‘h’. This makes the whole calculation easier.

____________

mean = 200 +[ ( -106 )/45 ]×20

= 200 - 47.11

= 152.89