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The formula we use for standard deviation depends on whether the data is being considered a population of its own, or the data is a sample representing a larger population.

The standard deviation formula may look confusing, but it will make sense after we break it down. In the coming sections, we'll walk through a step-by-step interactive example.

It's a way of quantifying how spread out the data is from its mean. A small standard deviation means that the data points are generally close to the mean, while a large standard deviation …

What is the average age of the bears at your zoo? What is the standard deviation? Round your answers to the nearest tenth.

The standard deviation formula may look confusing, but it will make sense after we break it down. In the coming sections, we'll walk through a step-by-step interactive example.

Practice calculating both sample and population variances.

Practice calculating the mean and standard deviation for the sampling distribution of a sample proportion.

You use it when you're finding the variance and only with a sample (vs. working with the universe, or all of the values.) The explanation is a little tricky to write, but if you're interested in knowing …

Reviewing the population mean, sample mean, population variance, sample variance and building an intuition for why we divide by n-1 for the unbiased sample variance. Created by Sal Khan.