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Alright guys, I've been scratching my head all day about my homework. I'm working with Microsoft Excel, specifically with standard deviation and its relationship to means. So I understand standard deviation fine and means fine, but I am now supposed to show the percentage of numbers that are within one (and two later) standard deviation(s) of the mean of those numbers. I have no idea how interpret these instructions into Excel's function window. Any help would be amazing.

The answer is 42.

I think my prof would get that but it wouldn't get me an A thanks though haha

This what your looking for?

http://www.gifted.uconn.edu/siegle/research/Normal/stdexcel.htm

Don't ask Dakka for help with your homework, it'll be a poor excuse later when you say that the "trolls have eaten your assignment"

I think he's trying to figure out how to work excel formulas for this, so thats ok. Lots of compu geeks on here.

Rangerrob wrote:This what your looking for?

http://www.gifted.uconn.edu/siegle/research/Normal/stdexcel.htm

Yes and no. I already know how to find the standard deviation and the mean, my problem is that I don't know how to develop a formula that shows what percentage of my numbers fall within 1 standard deviation of the mean (so (Mean+st.dev.) and (mean-st dev.).


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Frazzled wrote:I think he's trying to figure out how to work excel formulas for this, so thats ok. Lots of compu geeks on here.

Bingo

In which format do you have to show this to your teacher/tutor/whatever? If you don't have to show that you used formulae just type in the answers.
If it's as a graph put in all the numbers you used to get the mean, and put in vertical gridlines 1sd apart.
I have no idea about which formulae to use though, sorry.

Well, he didn't specify. I can't find anything regarding a formula, my assumption was that he would want a formula to show where I got my numbers. He doesn't want a graph though.

youngblood wrote:

Rangerrob wrote:This what your looking for?

http://www.gifted.uconn.edu/siegle/research/Normal/stdexcel.htm

Yes and no. I already know how to find the standard deviation and the mean, my problem is that I don't know how to develop a formula that shows what percentage of my numbers fall within 1 standard deviation of the mean (so (Mean+st.dev.) and (mean-st dev.).


Automatically Appended Next Post:

Frazzled wrote:I think he's trying to figure out how to work excel formulas for this, so thats ok. Lots of compu geeks on here.

Bingo

I'd skip the formula and make another three columns...with the something like...
Column 1) if # <= mean+st.dev then cell = 1,
Column 2) if # >= mean-st.dev then cell =1,
Column 3) add the cells for those two columns. Any row with a value of 2 (# falls in the range)

something like that...not sure if that is exactly right...but should point yah in the right direction.

Screw Excel, if you're going to determine Std Dev get the big boy's toy.
http://www.minitab.com/en-US/default.aspx

Gracias rangerbob. That's a great direction you have pointed me.

Hey I'm new, saw this thread when I was browsing for Indiana players.

If you have a normal distribution then percentages of your data follow a certain rule, call the 68-95-99.7 rule. I didn't name it okay ?

So if you add and subtract one standard deviation from the mean, then the range you get is 68% of you data.

If you add and subtract two standard deviations from the mean, that is 95% of your data etc.

Example:

Suppose you survey everyone on DakkaDakka to find out how many minis they paint a year. You find out that the mean is 100 minis and the standard deviation is 20 minis.

Therefore 68% of Dakkaites paint between 80-120 minis a year, and 95% of Dakkaites paint between 60-140 minis per year etc.

I've taken alot of math and I tutor a lot, so much so that I have an OCD tendency to answer people's math questions.

Hope that was helpful. I'm almost positive that is what your prof. is looking for. Try wiki if this is still unclear: http://en.wikipedia.org/wiki/Normal_distribution

Information that would be most helpful to you would be about half way down where it says "Standard Deviation and confindence intervals"

GS

That's progress for ya. I didn't even own a computer until I was 28, and I've never used Excel. Perhaps in my next life...

youngblood wrote:Gracias rangerrob. That's a great direction you have pointed me.

glad to help!

General specific, thank you! great explanation