NCERT Book Class 11 Maths Chapter 13 Statistics

Chapter 13

STATISTICS

v“Statistics may be rightly called the science of averages and their
estimates.” – A.L.BOWLEY & A.L. BODDINGTON v

13.1 Introduction
We know that statistics deals with data collected for specific
purposes. We can make decisions about the data by
analysing and interpreting it. In earlier classes, we have
studied methods of representing data graphically and in
tabular form. This representation reveals certain salient
features or characteristics of the data. We have also studied
the methods of finding a representative value for the given
data. This value is called the measure of central tendency.
Recall mean (arithmetic mean), median and mode are three
measures of central tendency. A measure of central
tendency gives us a rough idea where data points are Karl Pearson
(1857-1936)
centred. But, in order to make better interpretation from the
data, we should also have an idea how the data are scattered or how much they are
bunched around a measure of central tendency.
Consider now the runs scored by two batsmen in their last ten matches as follows:
Batsman A : 30, 91, 0, 64, 42, 80, 30, 5, 117, 71
Batsman B : 53, 46, 48, 50, 53, 53, 58, 60, 57, 52
Clearly, the mean and median of the data are
Batsman A Batsman B
Mean 53 53
Median 53 53
Recall that, we calculate the mean of a data (denoted by x ) by dividing the sum
of the observations by the number of observations, i.e.,