Calculate the confidence interval of a sample set. Enter the sample number, the sample mean, and standard deviation to calculate the confidence interval.
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Confidence Interval Formula
The confidence of a sample set can be calculated through the following formula:
X ± Zs√(n)
- Where X is the mean
- Z is the Z-Value
- s is the standard deviation
- n is the number of samples
The z-value or z-score can be calculated using the table below.
| Confidence Level | Z |
| 80% | 1.282 |
| 85% | 1.44 |
| 90% | 1.645 |
| 95% | 1.96 |
| 99% | 2.576 |
| 99.50% | 2.807 |
| 99.90% | 3.291 |
Confidence Interval Definition
A confidence interval is a type of estimate in statistics that shows a possible range of values for an unknown variable or parameter.
How to calculate a confidence interval?
Time needed: 10 minutes.
How to calculate a confidence interval?
- First, you need to calculate the mean of your sample set.
This can be done by summing the entire set of numbers and then dividing by the total numbers in the sample set. Another word for the mean is average.
- Next, you need to determine the z-score.
This is done through the use of the table above. Simply select the confidence level you wish to calculate the confidence interval at, and use the table to grab the z-value.
- Calculate the standard deviation
Standard Deviation Formula
- Finally, enter the values into the calculator.
Alternatively, you could simply enter the values into the formula and calculate using a normal calculator.
FAQ
A confidence interval is a type of estimate in statistics that shows a possible range of values for an unknown variable or parameter.
A confidence level is going to be chosen based on the statistics and outcomes being analyzed. If you have greater confidence in your data, choosing a higher confidence level.
A confidence interval is a range of values-based on the mean. As a result, the solution will be both the upper and lower bounds of that range of values.
