## Outlier Detection Methods

There are a few different outlier detection methods that you can use in order to find outliers in your data. Some popular methods include the IQR method, the Z-score method, and the Standard Deviation method.

### Standard Deviation Method

One of the most common outlier detection methods is the Standard Deviation Method. This method uses the standard deviation of a dataset to identify outliers. First, the mean and standard deviation of the data are calculated. Then, any data points that are more than three standard deviations away from the mean are considered outliers.

The Standard Deviation Method is a simple and effective way to find outliers in data. However, it does have some drawbacks. First, this method only works well on data that is normally distributed (bell-shaped). If the data is not normally distributed, the Standard Deviation Method may not produce accurate results. Second, this method is only effective at finding outliers that are far from the mean. It cannot find outliers that are close to the mean or in the middle of the data.

### Interquartile Range Method

One of the most common ways to detect outliers is by using the interquartile range (IQR) method. This approach involves computing the difference between the first quartile (Q1) and the third quartile (Q3). The IQR is then used to identify outliers as values that fall below Q1 – 1.5 * IQR or above Q3 + 1.5 * IQR.

One of the advantages of this method is that it is relatively easy to compute and understand. Additionally, because it only uses information about the distribution at the edges, it is less affected by moderate deviations from normality than other methods such as the standard deviation method.

However, there are also some drawbacks to this approach. One is that it is only appropriate for use with data that are roughly normally distributed. If your data are not normally distributed, you may want to use a different method. Additionally, this method is only appropriate for data that have no outliers. If your data does have outliers, you may want to use a different method such as the z-score method or the modified z-score method.

### Median Absolute Deviation Method

The median absolute deviation (MAD) method is a robust outlier detection method that is not influenced by outliers. The MAD is calculated by taking the median of the absolute values of the differences between the data points and the median. The MAD can be used to find outliers in both univariate and multivariate data sets.

### Grubb’s Test

Grubb’s test is a statistical procedure used to identify potential outliers in data. It is based on the idea that if a point is an outlier, it will be further away from the mean than most other points.

To conduct Grubb’s test, first calculate the mean and standard deviation of your data. Then, calculate the difference between each data point and the mean. These differences are called residuals. Next, square each residual. Finally, compare the squared residuals to a critical value. If a squared residual is greater than the critical value, it is considered an outlier.

There are two main types of Grubb’s tests: the 1.5 Sigma test and the 2 Sigma test. The 1.5 Sigma test is more liberal, meaning that it will identify more outliers than the 2 Sigma test. The 2 Sigma test is more conservative, meaning that it will identify fewer outliers.

Grubb’s tests are commonly used in quality control applications to identify potential issues with products or processes. They can also be used in research to identify potential outliers in data sets.

## Which of the following is not an outlier detection method?

There are a few different methods that can be used for outlier detection, but not all of them are created equal. Some methods are more accurate than others, and some are more suited for certain types of data. In this article, we’ll discuss which of the following is not an outlier detection method.

### The Mean Absolute Deviation Method

There are several different ways to detect outliers, and the Mean Absolute Deviation (MAD) method is one of the most popular. This method calculates the average deviation of each data point from the mean, and then identifies points that are significantly above or below this average. While MAD is a helpful tool for identifying outliers, it does have some limitations. For example, it can be biased by groups of outliers, and it is not effective at detecting certain types of outlier patterns. As such, it is important to use multiple outlier detection methods to get the most accurate results.

### The Z-Score Method

There are a few different ways to detect outliers, but the most common method is called the Z-Score method. To calculate the Z-Score of a data point, you take that data point’s distance from the mean, and divide it by the standard deviation. If the Z-Score is less than -3 or greater than 3, then that data point is considered an outlier.

Other methods for detecting outliers include the Interquartile Range (IQR) method and the Standard Deviation Method. The IQR method is used to find outliers in data that has already been sorted into quartiles. To do this, you take the difference between the first and third quartiles, and anything that falls outside of 1.5 times that difference is considered an outlier. The Standard Deviation method is similar to the Z-Score method, except you multiply the data point’s distance from the mean by 2 instead of dividing it by the standard deviation. If the result is greater than 2, then that data point is considered an outlier.

### The Chi-Square Method

There are a number of different statistical methods for detecting outliers in data, but the Chi-Square method is not one of them. The Chi-Square method is a statistical test that is used to compare two or more categorical variables, and it cannot be used to detect outliers.

### The Boxplot Method

In statistics, an outlier is a data point that is significantly different from the rest of the data. There are a number of ways to detect outliers, but one of the most common is the boxplot method.

To use the boxplot method, you first need to construct a boxplot. This is done by plotting the data points on a graph and then drawing a box around the middle 50% of the points. The remaining data points are then classified as outliers.

The Boxplot Method is a simple and effective way to detect outliers, but it does have some limitations. First, it can be difficult to decide what constitutes an outlier. Second, the method is not effective for detecting outliers in small data sets.