Skewness is a term used to measure the asymmetry of data distribution. The skewness value could be both negative and positive and it simply helps us in understanding the form of a distribution. Do you know how to calculate skewness in Excel?
Note that if the skewness value is negative, it identifies the tail position on the left side of the distribution that even expands towards more negative values. On the other hand, when the value of skewness is positive, it signifies the tail position on the right side that expands even towards more positive values.
Furthermore, when the value appears as zero, it means there is no presence of skewness in the distribution. It also tells us the distribution is symmetrical and it happens rarely.
How to Calculate Skewness in Excel?
Below is a built-in function of Excel that helps in analyzing the skewness of a dataset:
=SKEW(array of values)
To enable this function the following formula is used:
Skewness = [n/(n-1)(n-2)] * Σ[(xi–x)/s]3
The arguments used in this formula are as:
n= It shows the size of the sample.
Σ= It shows the “Sum” value.
xi = I t shows the Ith value in the dataset.
X= It shows the mean value.
S= It shows the standard deviation of data.
Well, you may consider the above formula a little difficult, however, Excel does it by itself and you don’t need to perform this function manually.
Several Methods to Measure a Skew:
Here are different methods to measure a Skew:
- Pearson Mode
- Bowley
- Momental
- Kelly’s Measure
Momental Skewness
Momental skewness helps in finding the skew of distribution and it is called Momental because of the mean value in statistics.
Below is the syntax given for calculating the Momental Skewness(y):
α(m) = 1/2 γ1 = μ3 / 2 σ3
μ: It shows the mean value.
σ= It shows the standard deviation.
γ = It shows the Fisher Skewness.
Momental Skewness Importance
Data understanding is the most important point when you need to apply some procedure. For instance, Pearson’s method can be applied only when you have the mean, mode, and standard deviation values. For this, Momental Skewness can help if the mean and standard deviation values are there.
Excel gives a positive or negative value while calculating skewness.
Below two options are explained to calculate skewness in Excel:
The Skew Function or Data Analysis:
Installing the Toolpak while working on the statistical project gives access to many other functions used in stats.
Skew Function
- Enter the data in Columns.
- Choose a blank cell from the worksheet.
- Add =AKEW(xx:yy)”
- In this formula, xx:yy is the cell location of data.
Data Analysis
- Click on the Data tab and choose “Data Analysis”.
- Select Descriptive Statistics and press OK.
- Simply click on the input Range box and put the data location.
- Click on the radio button for rows and columns.
- Choose the Labels in the first-row box when the data has column headers.
- Open the Descriptive Statistics.
- Choose a location for the output.
- Press OK.
How to Calculate Skewness With Data Analysis ToolPak Add-In?
To use this method, you need to install the Data Analysis ToolPal first. If you already have installed then follow the steps given below:
- Open the Data tab from the Ribbon.
- Click on the Data Analysis button.
- Click on the Descriptive Statistics option from the new window that appears.
- Click OK.
- You have to add parameters:
- Input Range: It is the range of your data.
- Labels in the first row: It is the labels in the data table.
- Output Range: It lets you choose where you need to get the skewness calculated.
- Summary Statistics: It needs you to check properly.
In row 10, you can see the skewness calculation and the result is not different than the first example.
When SKEW should be avoided in Excel?
There are some instances when using SKEW is not recommended at all. One such example is when you work with data that is unevenly distributed. It is because the SKEW function can produce wrong outcomes that’s why you don’t need to use it.
On the other hand, when the dataset is not big enough you should avoid using the SKEW function because this function does not prove to be reliable. Furthermore, the SKEW function should be avoided when you need to calculate the standard deviation because it is not the main thing you are supposed to do.
Summary:
In this post, you have learned how to calculate skewness in Excel by using multiple approaches. You can try any of the above methods because each method lets you understand the process in a better way.
