# Outlier

## Outlier :

An outlier is a data point that is significantly different from the other data points in a dataset. It can be caused by a variety of factors, including errors in measurement, extreme values, or simply being an unusual occurrence. Outliers can have a significant impact on the results of statistical analyses, so it is important to identify and address them appropriately.
Here are two examples of outliers:
Errors in measurement: Imagine you are conducting a study to determine the average height of people in a certain population. During the measurement process, you accidentally record one person’s height as 6 feet instead of 5 feet 6 inches. This data point would be an outlier because it is significantly different from the other data points and could potentially skew the results of your statistical analysis.
Extreme values: Imagine you are conducting a study to determine the average income of people in a certain population. One of the participants is a successful business owner who makes significantly more money than the other participants. This data point would be an outlier because it is significantly different from the other data points and could potentially skew the results of your statistical analysis.
It is important to identify and address outliers in statistical analyses because they can have a significant impact on the results. Outliers can cause statistical techniques to produce inaccurate or misleading results, and they can also affect the interpretation of the data. For example, if you are conducting a study to determine the average income of people in a certain population and you include an outlier data point of a business owner who makes significantly more money than the other participants, your calculated average income will be higher than it would be if you excluded the outlier data point.
There are several ways to identify and address outliers in statistical analyses. One method is to plot the data on a graph and visually inspect it for any unusual points. Another method is to calculate the standard deviation and mean of the data and identify any points that fall outside of two standard deviations from the mean. This is known as the “two standard deviation rule.”
Once an outlier has been identified, it is important to determine whether it should be included or excluded from the analysis. This decision should be based on the reason for the outlier and its potential impact on the results. If the outlier is caused by an error in measurement or an unusual occurrence, it may be appropriate to exclude it from the analysis. On the other hand, if the outlier is caused by an extreme value that is representative of the population being studied, it may be appropriate to include it in the analysis.
In summary, an outlier is a data point that is significantly different from the other data points in a dataset. It can be caused by a variety of factors, including errors in measurement, extreme values, or simply being an unusual occurrence. Outliers can have a significant impact on the results of statistical analyses, so it is important to identify and address them appropriately. This can be done through visual inspection of the data or using the “two standard deviation rule.” The decision to include or exclude an outlier should be based on the reason for the outlier and its potential impact on the results.