What you need today…  Pen/pencil  Calculator  Composition notebook  Histogram out from yesterday Schedule: Go over histograms Day 5: Standard Deviation Notes

Day 5: Unit 8: Standard Deviation Ms. Hall

What is Standard Deviation?  Let’s first define deviation:  Deviation means how ___ from the _______.  Now, standard deviation is…  It is the _______ amount that the values are _____ from the _______.  It is a ________ of how __________ the numbers are. farnormal average meanaway measurespread out

So who cares about standard deviation? What does all this blah blah blah mean anyways? Ever heard the phrase… “give or take a few”?

How many miles is Conway from Greenbrier? Standard deviation refers to the phrase, “give or take a few” when giving a guesstimate over a subject such as how many miles Conway is from Greenbrier. You might hear something like, “I think it’s 10 miles give or take a few.” Well, that “give or take a few” is the basic idea of standard deviation. It’s how much you are off from the average.

Step 1  Say we have a list of numbers of guesses of how far Conway is from Greenbrier: 9,2,5,4,12,7,8,11  Find the mean The mean is 7.25

Step 2  The mean is  Now for each number, _______ the mean and ______ the results. 9,2,5,4,12,7,8,11 subtract square Answers: , , , , ,.0625,.5625,

Step 3  Find the mean of those _________________ squared differences , , , , ,.0625,.5625, Mean of the squared differences:

Step 4  Finally, take the square root of that and you’re done!  Now, let’s do another example. Mean of the squared differences: Square root of rounded to nearest hundredth is 3.23

Example  Ten friends scored the following scores on the end of the year math exam: 23%, 37%, 45%, 49%, 56%, 63%, 63%, 70%, 72%, 82% Step 1: mean is 56 Step 2: 1089, 361, 121, 49, 0, 49, 49, 196, 256, 676 Step 3: mean of Step 2 is Step 4: square root of Step 3 is 16.87

The Formula Explained CHECK OUT WHAT YOU JUST DID!!! mean

You have one homework problem due tomorrow.