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Operations Research, Systems Engineering and Industrial Engineering *Commons*^{™}

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Articles **1** - **2** of ** 2**

## Full-Text Articles in Operations Research, Systems Engineering and Industrial Engineering

Why Divide By (N-1) For Sample Standard Deviation?, Paul Savory

#### Why Divide By (N-1) For Sample Standard Deviation?, Paul Savory

*Industrial and Management Systems Engineering -- Instructional Materials*

In statistics, the sample standard deviation is a widely used measure of the variability or dispersion of a data set. The standard deviation of a data set is the square root of its variance. In calculating the sample standard deviation, the divisor is the number of samples in the data set minus one (n-1) rather than n. This often confuses students. This paper offers a quick overview of why the divisor is (n-1) for calculating the sample standard deviation.

How Do You Interpret A Confidence Interval?, Paul Savory

#### How Do You Interpret A Confidence Interval?, Paul Savory

*Industrial and Management Systems Engineering -- Instructional Materials*

A confidence interval (CI) is an interval estimate of a population parameter. Instead of estimating the parameter by a single value, a point estimate, an interval likely to cover the parameter is developed. Many student incorrectly interpret the meaning of a confidence interval. This paper offers a quick overview of how to correctly interpret a confidence interval.