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717richboy's avatar

Statistics question. Finding the standard deviation for these numbers: 1, 2, 98, 100, 105.

Asked by 717richboy (234 points ) September 26th, 2012

There isn’t enough information provided in order to calculate the standard deviation, correct? I’m working on statistics, and I think it’s a trick question; there is no standard deviation.

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6 Answers

PhiNotPi's avatar

Hint: There aren’t going to be any trick questions in statistics. There is enough information to calculate the standard deviation.

717richboy's avatar

How do I calculate it? I appreciate the help.

PhiNotPi's avatar

Consider this set of numbers: {2,4,4,4,5,5,7,9}

The first step is to find the mean of the numbers, which is x` = 5. (x` is read as “x bar” and represents the mean)

Then, for each number in the set, you calculate the following: (x – x`)^2
(2 – 5)^2 = 9
(4 – 5)^2 = 1
... = 1
... = 1
... = 0
... = 0
... = 4
(9 – 5)^2 = 16

Now add these up (32) and divide by n-1, where n is the number of numbers (n is 8, so 7).
32 / 7 ~= 4.571428…

Now square root this.

Sample Standard Deviation = 2.138

Kayak8's avatar

@PhiNotPi Major kudos for typing that into a little square and explaining it very clearly!

717richboy's avatar

Thank you so much!

emeraldisles's avatar

I actually understood how you got that as an answer. I wish you could explain math to me.

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