A normal probability plot, whether on probability paper or not, can help you decide whether a set of values are from a normal distribution. To make this determination, you must apply the probability of a normal distribution, which, if you were doing it by hand, is where probability paper comes in. While Microsoft Excel doesn't have an actual print layout for probability paper, there are adjustments you can make to a chart to simulate this format.

## Step 1: Enter Data Set

You have data that are the results of a small sampling and you want to know whether these data are from a normal distribution. **Open Excel** and **enter** the data on a worksheet.

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#### Tip

It's always a good idea to save your work, the Excel workbook, after completing each step of this, or any, process.

## Step 2: Select the Data for Sorting

**Select** the data to be sorted by clicking into the cell with the first value (not the heading) and, while **holding** the mouse button down, **move** the mouse pointer down to the last value and **release** the button. The data cells should be shaded now, which means they are "selected."

## Step 3: Sort the Data

**Click** on the Home tab of the Excel Ribbon and **click** the Sort & Filter button to display its menu. **Click** on Sort A to Z (or low to high)to sort the data selected in the previous step.

## Step 4: Number the Values

In a column adjacent to the data values, **enter** a sequence number, from top to bottom, for each of the values, numbering them from 1 to *n*, which in the example n = 13.

## Step 5: Calculate the Mean

In a blank cell on the same worksheet as the data, **enter** the AVERAGE() function to compute the arithmetic mean of the data set:

**=AVERAGE(First_Cell:Last_Cell)**

First_Cell and Last_Cell refer to the beginning and ending cells of the data value range. In the example, the function statement is =AVERAGE(B2:B14)**.**

#### Tip

You may want to assign a header or label to this and other computed values for later reference.

## Step 6: Calculate the Standard Deviation

Adjacent to the cell in which you calculated the mean, enter the STDEV() function to calculate the standard deviation of the values in the data set:

=STDEV**(First_Cell:Last_Cell)**

First_Cell and Last_Cell refer to the beginning and ending cells of the data value range. In the example, the function statement is =STDEV(B2:B14)**.**

#### Tip

STDEV and STDEVP are functions for use on data samples. STDEV

## Step 7: Calculate the Cumulative Probabilities

Enter the NORMDIST() function to complete the cumulative probability of each value.

To complete the data needed to create a plot, the values need to be numbered in sequence, the associated z-value determined and the probability of each value along with a cumulative probability of all the values.