When you want to gather any formation based on a large population, things get difficult sometimes to capture this huge number of people. In that case, we tend to go for the **confidence interval** which is calculated for a small group of people, that represent the whole population. In **Microsoft Excel**, we can easily **calculate the confidence interval** based on their proportion. Therefore, in this article, we will guide you on how to **calculate confidence interval proportion** in excel with 2 useful examples.

## Download Practice Workbook

Get this sample file to try the process by yourself.

## What Is Confidence Interval?

Before starting the calculation, we must understand the **confidence interval **first. According to statistics, it is basically a probability of a specific parameter that falls between a couple of values. **Confidence interval **measures the level of certainty of uncertainty in a trial process.

Now, in the case of **proportion**, the **confidence interval** provides a range of values that contains a proportion of the population with a level of confidence in a specific sample test. The values show the** confidence interval proportion** for both high and low estimations.

## Mathematical Formula of Confidence Interval for Proportion

To calculate the confidence interval for proportion, we have to use this formula.

**Confidence Interval = pÂ +/-Â z*âˆšp(1-p) / n**

Here,

**p = Proportion of Success**

**z = Chosen z-Value**

**n = Sample Size**

In the formula, the** z-value **is dependent on the confidence level which generally differs from **90%** to **99%**. Moreover, the relationship between the** z-value** and the **confidence interval **is always proportional. The **confidence interval for proportion **is always calculated for both the **upper **and** lower bound**.

## 2 Useful Examples of Calculating Confidence Interval for Proportion in Excel

Finally, we will start calculating the confidence interval for proportion with 2 examples. Here, we will do the calculation with the mathematical formula that we described above. Along with it, we will also apply the Excel formula for the calculation. So, without further delay, letâ€™s go through the calculation.

### Example 1: Find Confidence Interval Proportion with Excel Formula

To illustrate the process, let us assume we have run a survey on** 100 students** to find out the proportion of their acceptance of the new curriculum. Seems like, out of **100**,** 56 students **have agreed on the new curriculum with a** confidence level **of** 95%**. Now, taking these parameters, let us find out the confidence interval for the proportion of this case.

- In the beginning, insert the values of
**Sample Size**,**Number of Confidence Levels**and rate of**Confidence Level**in the**cell range C5:C7**.

- Then, calculate the
**Proportion of Success**with this formula in**cell C8**and press**Enter**.

`=C6/C5`

- Along with it, find out the
**Proportion of Failure**as well in**cell C9**. - For this, type this formula and hit
**Enter**.

`=1-C8`

- Now, calculate the
**Alpha**value based on the**Confidence Level**with this formula in**cell C10**.

`=1-C7`

- Following, press
**Enter**.

- Next, type this formula in
**cell C11**and press**Enter**to**get the z-value for a 95% Confidence Level**.

`=ABS(NORM.S.INV((C10)/2))`

**the NORM.S.INV**

**function**is used to return the inverse value of

**cell C10**. along with it, we attached

**the ABS function**to get an absolute value.

- Lastly, insert this formula to get the
**Margin of Error**for proportion in**cell C12**.

`=C11*SQRT(C8*C9/C5)`

**the SQRT function**is used to square root the output of calculation between

**cells C8**,

**C9**and

**C5**.

- Lately, hit
**Enter**and you will get all the parameters that we will need for the final calculation.

- Now, type this formula in
**cell C14**to calculate the**Upper Bound**.

`=C8+C12`

- Also, apply this formula for calculating
**Lower Bound**in**cell C15**.

`=C8-C12`

- Finally, hit
**Enter**. - Thatâ€™s it, you can now see the true proportion of the confidence interval based on the survey.

**Read More:** **How to Calculate 95 Percent Confidence Interval in Excel (4 Ways)**

### Example 2: Calculate Confidence Interval Proportion with Mathematical Formula

In this section, we will take the same case scenario for calculation. The only difference is that we will find out the proportion of the confidence interval by calculating it with the mathematical formula. Letâ€™s see how it works.

- First, insert all the parameters up to
**z-Value**in the**cell range B5:C11**that we got from the example above.

- Now, insert this mathematical formula in
**cell C12**to calculate the**Margin of Error**.

`=C11*((C8*C9)/C5)^0.5`

- After this, hit
**Enter**to get the output.

- Next, type this formula in
**cell C14**to calculate**Upper Bound**.

`=C8+C12`

- Lastly, get the
**Lower Bound**value in**cell C15**with this formula.

`=C8-C12`

- Finally, hit
**Enter**. - Thatâ€™s it, you can see that the true proportion values of confidence intervals are the same for any type of formula.

**Read More: ****How to Find Confidence Interval in Excel for Two Samples**

## How to Calculate Confidence Interval for Difference in Proportion in Excel

So far, we calculated the confidence interval for a single bunch of students. Let us consider now two groups of students where each group has **100 people**. But the **confidence levels **are **56** and **46 **respectively. The basic formula to calculate the difference is as follows,

**Confidence interval = (p1â€“p2)Â +/-Â z*âˆš(p1(1-p1)/n1 + p2(1-p2)/n2)**

Where,

**p1, p2 = Proportion of sample 1 and sample 2**

**n1, n2 = Sample size of sample 1 and sample 2**

Now, we will calculate the confidence interval for the difference in proportion among these two groups for a **confidence level rate **of **95%**.

- First, insert all the parameters for each group in the
**cell range B5:E12**.

- Then, type this formula in
**cell C14**to get the difference in**Upper Bound**.

`=(C8-E8)+(C12+E12)`

- Press
**Enter**. - Lastly, insert this formula to calculate the difference of proportion in the
**Lower Bound**in**cell C15**.

`=(C8-E8)-(C12+E12)`

- Finally, hit
**Enter**. - Thatâ€™s it, you will get the difference in proportion between the two groupsâ€™ acceptance of the new curriculum.

**Read More: ****How to Find Upper and Lower Limits of Confidence Interval in Excel**

## Conclusion

Concluding the article, I hope that you have got a clear understanding of how to calculate confidence interval proportion in excel with 2 useful examples. Let us know your insightful suggestion in the comment box. Keep learning Excel with **ExcelDemy**.

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