Confidence (Confidence Interval)

Returns the confidence interval for a population mean. The confidence interval is a range of values on either side of a mean. For example, if you order a product through the mail, you can determine, within a given level of confidence, the earliest and latest date of expected arrival.

Syntax

Confidence(Alpha, Stdev, Size)

Where:

Alpha is the level of significance at which confidence is computed.

Stdev is the standard deviation of the population for the given data range.

Size is a positive integer indicating the size of the sample.

Expression

The confidence level is expressed as [100(1-alpha)%]. If alpha = 0.05, then:

• Confidence = 95%
• The area equivalent to 95% of the population = 1.96
• The confidence interval is

Usage Notes

If size is not an integer, it is truncated.

The following conditions are invalid:

• One of the arguments is nonnumeric.
• alpha < 0 or alpha > 1
• stdev < 0
• size < 1

Example

For an example of the Confidence function, see Confidence level example.