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CONFIDENCE.NORM

The CONFIDENCE.NORM formula is a statistical function that calculates the confidence interval for a given population mean, based on a normal distribution. It is commonly used to determine the sample size required to estimate a population mean within a specific margin of error with a given level of confidence.

Usage

Use the CONFIDENCE.NORM formula with the syntax shown below, it has 3 required parameters:

=CONFIDENCE.NORM(alpha, standard_deviation, pop_size)
Parameters:
  1. alpha (required):
    The significance level used to calculate the confidence interval. It must be a number between 0 and 1.
  2. standard_deviation (required):
    The population standard deviation. It must be a positive number.
  3. pop_size (required):
    The size of the population. It must be a positive integer.

Examples

Here are a few example use cases that explain how to use the CONFIDENCE.NORM formula in Google Sheets.

Estimating sample size for a survey

You want to conduct a survey to estimate the average income of a population with a margin of error of $100 and a 95% level of confidence. You can use the CONFIDENCE.NORM formula to determine the required sample size.

Estimating production yield

You are responsible for quality control in a factory and want to estimate the average yield of a production process with a margin of error of 2% and a 99% level of confidence. You can use the CONFIDENCE.NORM formula to determine the required sample size.

Estimating student performance

You want to estimate the average grade of a student population with a margin of error of 0.5 and a 90% level of confidence. You can use the CONFIDENCE.NORM formula to determine the required sample size.

Common Mistakes

CONFIDENCE.NORM not working? Here are some common mistakes people make when using the CONFIDENCE.NORM Google Sheets Formula:

Not specifying alpha

If alpha is not specified, the formula will return a confidence interval with a default alpha of 0.05. To specify a different alpha value, make sure to include it as the first argument in the formula.

Using sample standard deviation

CONFIDENCE.NORM requires the population standard deviation as an input, not the sample standard deviation. To calculate the population standard deviation, use the STDEVP function.

Incorrectly specifying population size

Make sure to correctly specify the population size as the third argument in the formula. If the population size is unknown, use a large number such as 1000000.

Related Formulas

The following functions are similar to CONFIDENCE.NORM or are often used with it in a formula:

  • STDEV.P

    The STDEV.P function is a statistical function that calculates the standard deviation of a population based on a sample of numerical data. It is commonly used to measure the amount of variation or dispersion in a dataset. The formula assumes that the input values represent the entire population, rather than a sample. If the input values represent a sample, you should use the STDEV.S function instead.

  • AVERAGE

    The AVERAGE function calculates the average (arithmetic mean) of the values passed to it. It is commonly used to find the average of a range of cells containing numerical data.

  • NORM.INV

    The NORM.INV function returns the inverse of the cumulative normal distribution for a specified mean and standard deviation. It is commonly used in statistical analysis to find the value at which a specified percentage of observations occur below that value.

Learn More

You can learn more about the CONFIDENCE.NORM Google Sheets function on Google Support.