019. Measures of central tendency and dispersion. Introduction

A data set of Quantitative variables can be also called as Variational series (Series of order statistics). Variant is a parameter point which varies. Frequency is the number of each variant. A data set of Qualitative variables called Attributive series. The purpose of this chapter is to determine various ways in which the average of a data set can be calculated. These averages are referred to as Measures of central tendency. It will be also explored ways to judge the extent to which the individual observations in a data set are spread out around their central point. These valuations of spread are called Measures of dispersion. A measure of central tendency locates the center, or average, of a data set. A measure of dispersion indicates the tendency for the individual observations to deviate from that center point. These important measures can be calculated for raw, ungrouped data, or for data that have already been grouped into classes within a frequency table. These objectives can best be achieved by examining the

- Mean, median, and mode for grouped and ungrouped data.

- Mean absolute deviation.

- Variance and standard deviation for grouped and ungrouped data.

- Quartiles, deciles, and percentiles for grouped and ungrouped data.

It might be easier to first compute the measures of central tendency for ungrouped data.

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