# 36. Statistics – Statistics Introduction

In Quality Assurance, statistics and data are always solid information to prove or validate the effectiveness or implementation. That is why understand statistics’ definition and how to interpret the statistic result is extremely critical to make the right calls. This section will talk about intro level of statistics’ definition and the common phrases or terms which are frequently used in statistics.

Statistics have the following definition based on the collected resource, which is either describe observations from objects (**descriptive statistics**) or use collected **sample** data to estimate the **population** status (**inferential statistics**).

Based on the collection from sample, variables can also be listed in the following lists for the common terms.

Variables which are discrete such as gender, religion or others which can be categorized

Variables which are continuous where as the value can be lay in between a finite range.

After the data are gathered for data description, measures of central tendency and measures of variability will be observed to evaluate or illustrate the data

In measure of central tendency, mean, median and mode are the most common phrases. The following table and list below will explain the differences between these definition.

*Mean Definition and Application*

When arrange the numbers from small to large, the median number is the middle number.

For instance, when you have 5 numbers laid out from small to large, then the 3rd number will be your median.

Mode is the value which appears the most in the data. So if the data consists of 1, 1, 3, 6, 9, 9 , 9. Then the mode for this data is 9.

By looking at measures of variability, indicators such as variance, standard deviation, ranges and mean absolute deviation are the primary focus for the data distribution and variance evaluation.

*Variance & Standard Deviation’s Equation Setup and Excel Function Calls*

*Range and Mean Absolute Deviation Setup and Excel Function Calls*