The variance is always calculated with respect to the sample mean.Ī general definition of variance is that it is the expected value of the squared differences from the mean. Thus, the sample variance can be defined as the average of the squared distances from the mean. In such a case, a select number of data points are picked up from the population to form the sample that can describe the entire group. Sample Variance - If the size of the population is too large then it is difficult to take each data point into consideration. It is used to give the squared distance of each data point from the population mean. When we want to find how each data point in a given population varies or is spread out then we use the population variance. Population Variance - All the members of a group are known as the population. The sample and population variance can be determined for both kinds of data. On the other hand, if data consists of individual data points, it is called ungrouped data. When data is expressed in the form of class intervals it is known as grouped data. ![]() ![]() ![]() Data can be of two types - grouped and ungrouped. A measure of dispersion is a quantity that is used to check the variability of data about an average value.
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