**The manual calculation process of the Z score:**

** Steps:**

- Choose a dataset. Here, we use a simple dataset with
**five values:****82**,**77**,**85**,**78**, and**80**. - Estimate the simple
*Mean*of this dataset.

- Evaluate the
*Standard Deviation*of our data. - The standard deviation is 2.87, which indicates that the dataset is normally distributed.

- Choose your desired confidence level interval. For our data, we set it at
**95%**. - In the
**Z-Score chart**, we must find the value of**0.975**(e.g.,**0.95+(0.05/2)=0.975**). - You may notice that the
*Vertical Axis*value for**0.975**is**1.9**and the*Horizontal Axis*value is**0.06**.

- Our
**95% confidence interval Z-score value**will be**1.9+0.06****= 1.96**.

We can estimate the **Z score** with a **95** confidence interval manually.

## Step-by-Step Procedure

### Step 1: Calculate the Mean of the Dataset

- Select cell
**F5**. - Enter the following formula in the cell:

`=AVERAGE(C5:C14)`

- Press
**Enter**.

- You will get the mean value of our dataset.

### Step 2: Estimate Standard Deviation

- Select cell
**F6**. - Enter the following formula in the cell:

`=STDEV.P(C5:C14)`

- Press
**Enter**.

- You will get the value of the
*Standard Deviation*. - You may notice that the
*Standard Deviation*is**2.914**. We can decide whether our dataset will be normally distributed.

### Step 3: Define the Confidence Interval Level

- Title cells
**E7**and**E8**as**Confidence level**and**Alpha**.

- In cell
**F7**, define the**C****onfidence****level**. Here, we define our confidence interval as**95%**.

- Enter the following formula to get the
**Alpha**value in cell**F7:**

`=1-F7`

- Press
**Enter**.

### Step 4: Estimate the Z Score for the Desired Confidence Interval

- Select cell
**F10**. - Enter the following formula in the cell:

`=ABS(NORM.S.INV((F8)/2))`

- Press
**Enter**.

- You will get the
**Z score**value with a**95 confidence**interval level**,**equal to the manual procedure.

** Breakdown of the Formula**

We are breaking down the formula for cell **F10**.

` `

**NORM.S.INV((F8)/2)**: The **NORM.S.INV** function gives us the **Z-score** value of **0.025**. The value will show a negative sign as this interval level is at the right side of the mean position. Here, the function returns **-1.960**.

` `

**ABS(NORM.S.INV((F8)/2))**: The **ABS** function will show the absolute value of the result of the **NORM.S.INV** function. For this cell, the function returns **1.960**.

**Read More: **How to Calculate Critical Z Score in Excel

**Download the Practice Workbook**

Download this workbook for practice.

## Related Articles

- How to Calculate Altman Z Score in Excel
- How to Calculate P Value from Z Score in Excel
- How to Calculate Probability from Z-Score in Excel

**<< Go Back to Statistical Significance in Excel | Excel for Statistics | Learn Excel**