ncert books for class maths cbsc

estimates.” – A.L.BOWLEY & A.L. BODDINGTON v . 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 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 : , , , , , , , , , Batsman B : , , , , , , , , , Clearly, the mean and median of the data are Batsman A Batsman B Mean Median 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.,