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  5. Intro to Statistics with R: Introduction

Exercise

Sample variance formula

In the video, you learned the following simple formula for variance:

$$\frac{\sum (X - M)^2}{N}$$

In practice, we'll often divide by \(N-1\) rather than \(N\) for reasons that are beyond the scope of this course. For now, just know that it's called the population variance when you use \(N\) and the sample variance when using \(N-1\) and you'll almost always use the sample variance when working with real data. Here's the formula for sample variance:

$$\frac{\sum (X - M)^2}{N - 1}$$

In this example, we have collected a sample of incomes for three people: $100, $300, and $500. Which of the following formulas would you use to calculate the variance of these incomes?

Instructions

50 XP

Possible answers