MS Excel - CONFIDENCE.NORM() function
Description
The Excel CONFIDENCE.NORM() function is used to get the confidence interval for a population mean, using a normal distribution. The confidence interval is a range of values. Your sample mean, x, is at the center of this range and the range is x ± CONFIDENCE.NORM.
Version: Excel 2013
Syntax
CONFIDENCE.NORM(alpha,standard_dev,size)
Parameters
| Name | Description | Data Type | Required/ Optional |
|---|---|---|---|
| Alpha | The significance level used to compute the confidence level. The confidence level equals 100*(1 - alpha)%, or in other words, an alpha of 0.05 indicates a 95 percent confidence level. | number | Required |
| A standard_dev | The population standard deviation for the data range and is assumed to be known. | number | Required |
| Size | The sample size. | number | Required |
Remarks :
- If any argument is nonnumeric, CONFIDENCE.NORM returns the #VALUE! error value.
- If alpha ≤ 0 or alpha ≥ 1, CONFIDENCE.NORM returns the #NUM! error value.
- If standard_dev ≤ 0, CONFIDENCE.NORM returns the #NUM! error value.
- If size is not an integer, it is truncated.
- If size < 1, CONFIDENCE.NORM returns the #NUM! error value.
- If we assume alpha equals 0.05, we need to calculate the area under the standard normal curve that equals (1 - alpha), or 95 percent. This value is ± 1.96. The confidence interval is therefore:
Example : Excel CONFIDENCE.NORM() function
The following worksheet shows confidence interval for a population mean. In other words, the confidence interval for the underlying population mean for travel to work equals 30 ± 0.692952 minutes, or* 29.3 to 30.7 minutes.
| Sample Data | Description |
|---|---|
| 0.05 | Significance level |
| 2.5 | Standard deviation of the population. |
| 50 | Sample size. |
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Source:http://www.w3resource.com/excel/excel-confidence-dot-norm-function.php
