How to Create a Normal Probability Plot in Excel (Step-by-Step)

A normal probability plot can be used to determine if the values in a dataset are roughly normally distributed.

This tutorial provides a step-by-step example of how to create a normal probability plot for a given dataset in Excel

Step 1: Create the Dataset

First, let’s create a fake dataset with 15 values:

Step 2: Calculate the Z-Values

Next, we’ll use the following formula to calculate the z-value that corresponds to the first data value:

=NORM.S.INV((RANK(A2, \$A\$2:\$A\$16, 1)-0.5)/COUNT(A:A))

We’ll copy this formula down to each cell in column B:

Step 3: Create the Normal Probability Plot

Next, we’ll create the normal probability plot.

First, highlight the cell range A2:B16 as follows:

Along the top ribbon, click the Insert tab. Under the Charts section, click the first option under Scatter.

This automatically produces the following chart:

The x-axis displays the ordered data values and the y-value displays their corresponding z-values.

Feel free to modify the title, axes, and labels to make the plot more aesthetically pleasing:

How to Interpret a Normal Probability Plot

The way to interpret a normal probability plot is simple: if the data values fall along a roughly straight line at a 45-degree angle, then the data is normally distributed.

In our plot above we can see that the values tend to deviate from a straight line at a 45-degree angle, especially on the tail ends. This likely indicates that the data is not normally distributed.

Although a normal probability plot isn’t a formal statistical test, it offers an easy way to visually check whether or not a data set is normally distributed.

If you’re looking for a formal normality test, read this tutorial on how to perform a normality test in Excel.

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3 Replies to “How to Create a Normal Probability Plot in Excel (Step-by-Step)”

1. Victor says:

This method or equation doesn’t work because I used the same numbers as the example and I get -1.28155 on each column.

2. Chee says:

Hi Zach, any particular reason why you chose -0.5 in the formula for NORM.S.INV((RANK(A2, SA\$2:\$A\$16, 1)-0.5/COUNT(A:A))

Thanks.

3. ยืนต้น says:

ว้าวดีครับผม สุดยอดสุดๆไปเลยครับผมนะ แต่ว่านะผมว่ามันจะดีกว่านี้นะครับนะ ถ้ามีการอธิบายสูตรนะครับเนี่ย