# Descriptive Statistics

**Basics of Descriptive Statistics**

**Descriptive statistics**provides a summary and analysis of a data collected from an experiment or study.- It is divided into two broad categories:
**measures of central tendency**and**measures of dispersion or variability**.

**Measures of Central Tendency**

**Mean**: It is the average of the data set and it’s calculated by adding all data points and dividing by the number of data points.**Median**: The median is the middle value that separates the higher half from the lower half of a data set. If the data set has an even number of observations, the median is the average of the two middle numbers.**Mode**: The mode is the value that appears most frequently in a data set.

**Measures of Dispersion or Variability**

**Range**: The range of a data set is the spread, which is the difference between the highest and lowest values.**Variance**: Variance measures how far each number in the set is from the mean (or expected value).**Standard deviation**: The standard deviation is the square root of the variance and provides a measure of the amount of variation or dispersion of a set of values.

**Visual Tools for Descriptive Statistics**

**Histograms and bar graphs**: These are visual representations of numerical data divided into bins or classes.**Box-and-whisker plots**: These plots visually show the median, lower and upper quartiles, and any possible outliers in the data.**Scatter plots**: These plots can visually display possible correlations between two different data sets.

**Rules & Principles**

- Use
**descriptive statistics**to summarize and interpret data but it does not allow you to make conclusions about the population that the data are taken from. **Outliers**can significantly affect the mean and the standard deviation, but have less impact on the median or mode.

**Importance & Relevance**

**Descriptive statistics**provide clarity to large amounts of data by reducing lots of data into a simpler summary.- These statistics help us understand and describe the features of a specific data set, providing an informative summary of the measure.