# Standard Deviation

Last updated 9 years ago

Discipline:
Math
Subject:
Algebra I
8   The Coral Reefs

Standard DeviationThis is the spread of the data. It tells you how close or far apart the data is from the average!

Using Your CalculatorStep1) Hit [STAT], "Edit"Step2) Type your data into L1Step3) Hit [STAT], arrow over to the "Calc" tab and select "1-Var Stats"

The x with the bar above it is the mean of the data, or the average. The rx symbol is your standard deviation

But what about Variance?Variance is just standard deviation squared. It's the spread of the data....squared!

EXAMPLE!A researcher at the aquarium calculated how many pieces of fish food the fish swimming through the coral ate per hour. The data is what they counted per hour in a day5 5 6 7 9 10 11 11 12 14

If we wanted to calculate the standard deviation by hand, then we would first find the mean, then subtract it from each data point. Next you square each data point, and find the new mean. This gives you the variance. Take the square root of that, and you have your standard deviation. That's a lot of work!

Symbols

= mean (average)

Using the calculator, we get a mean of 9, a standard deviation of 3.1, and a variance of 9.7