programming forums Java Mobile Certification Databases Caching Books Engineering Micro Controllers OS Languages Paradigms IDEs Build Tools Frameworks Application Servers Open Source This Site Careers Other all forums
this forum made possible by our volunteer staff, including ...
Marshals:
• Campbell Ritchie
• Ron McLeod
• Paul Clapham
• Bear Bibeault
• Junilu Lacar
Sheriffs:
• Jeanne Boyarsky
• Tim Cooke
• Henry Wong
Saloon Keepers:
• Tim Moores
• Stephan van Hulst
• Tim Holloway
• salvin francis
• Frits Walraven
Bartenders:
• Scott Selikoff
• Piet Souris
• Carey Brown

# standard deviation of any sized array java

Greenhorn
Posts: 14
Hey guys I'm having trouble figuring out how to calculate the standard divination of an array in Java. As you can see I have already calculated the mean, and I know that at the end I will have to divide by the sample size minus 1 (n-1) and square that number. The problem I'm having is how to take every number and calculate how far it is away from the mean, then square that number. I know I could do every number from the data set separately but there has to be an easier way. Any help would be appreciated, here's my code.

Marshal
Posts: 25805
69
Is your problem that you don't know what is meant by "how far it is away from the mean"? You'd take the number and subtract the mean, that's how. (Calling the variable which stores the mean value "average" wasn't a good choice, by the way.)

And yes, you do have to do that for each data point in the sample. So putting it inside the loop like you did, you're on the right track.

lowercase baba
Posts: 12893
63
There is probably a package you can download that would have everything you need in it, but I'm guessing you are supposed to do this yourself.

The first steps when writing a program should always be to think through how you'd do it yourself, with pencil and paper. In order to figure out how far a number is from the mean, you need two things: the number, and the mean.

And you can't get the mean until you have looked at every number.

So yes, you do need to loop through your array (at least) twice. Once to get the mean, and once to get the difference between each number and the mean. There is no way to do it in one pass.

 No more fooling around. Read this tiny ad: Building a Better World in your Backyard by Paul Wheaton and Shawn Klassen-Koop https://coderanch.com/wiki/718759/books/Building-World-Backyard-Paul-Wheaton