Page 1 - Lession note - stat chap -9,MCT (AM)-51

Class-XI

STATISICS

CHAPTER-Measures of Central Tendency

Topic –Arithmetic Mean (Module-51)

Open ended, combine mean , corrected mean and weighted mean

Short note

Arithmetic Mean
Arithmetic Mean is the number which is obtained by adding the values of

all the items of a series and dividing the total by the number of items.

Calculation of Weighted Mean
According to this way, we find weighted mean from the following information

Combines Mean =

Corrected Mean : CORRET = CORRET TOTAL / N

CORRECT TOTAL = INCORRECT TOTAL - INCORRECT VALUES + CORRECT
VALUES

INCORRECT TOTAL = * N

Examples 1:- Find the AM of the following open ended series .

X Below 10 10-20 20-30 30-40 40-50 Above 50
f 2 4 3 2 5 2

Examples 2:- Find the weighted mean of the following .

X 0-10 10-20 20-30 30-40 40-50 50-60
w 2 4 3 2 5 2

Example 3:- Question on combine mean

The average rainfall of a city from Monday to Saturday is 0.3 cms .Due to heavy
rainfall on Sunday, the average for the whole week rose to 0.5 cms . How much was
the rainfall on Sunday? Ans : 1.7cms

Example 4 : -