In the previous chapter we covered a number of statistics concepts and others that are worth remembering. We'll briefly review them here, but if these concepts are new to you, please review Lesson 5. 

 

Average (mean): The sum of all of the values divided by the number of values. The mean can be a useful tool for quickly summarize your data. However, the mean is an incomplete picture of what your distribution actually looks like. Specifically, it gives a sense of where the center of the data is, but not the spread of the data (how widely the values range).

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Range (spread): The distance between the largest number in a set and the smallest number.

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Standard Deviation: The difference in spread can be quantified by something called the “standard deviation.” For now, the details of how this is calculated don’t matter. The intuition is that for each value, we calculate how far it is from the mean and then combine all those differences together into a single number the standard deviation). Therefore, if many of the values are far from the mean, we get a big standard deviation, meaning that the spread of the values is high. Alternatively, if most of the values are close to the mean, we will get a small standard deviation, and that means that the spread is narrow.