Statistic rooky needs help with correlation

I haven't a clue, but this doesn't appear to be spam so I'll give it a bump.

Maybe a satitsitc... a stastic.... a numbers person will see this.

BUMP!

FIrst, what's your hypothesis? Once you've got a hypothesis you'll want to do a Chi-square analysis.

Set your data up in a 2-by-2 table.

This Link explains it pretty well.

You can report out the results of the significance of the chi-square based on the degrees of freedom for your data (see link) or you can express it in terms of an odds ratio. There are online calculators for both chi-square and odds ratio calculations. Here's one for an odds ratio http://www.vassarstats.net/odds2x2.html

What are you trying to understand? Are you asking whether Diagnosis A or B is better in predicting the presence of the virus?

The best way to do this is to stick it into a statistical package and generate a model. It takes five minutes and the answer is there is not a statistical difference between diagnoses A and B to a 95% confidence interval. If you want to do it manually, you should seek medical help. Ok, that was a bad pun. You can create a model that looks something like:

Virus = m * Diagnosis + b

Where Virus = 1 or 0 for yes or no, diagnosis = 1 or 0 for A or B and m and b are your standard variables for fitting a line. You can fit the line in Excel or by hand to find the slope and intercept, but what is important is the F statistic on the slope. That will show you significance. The question you need to answer is "Is this line any different than just a flat line" because a flat line means no significance at all. You can then use an online app or a statistics table to see whether that value is significant. In this case, it is not.

That's a great link! You can enter your data directly into a table there and get the Chi square statistic right away! Also a lot faster than my technique. Still same answer but a lot faster.

The breadth of knowledge on A2K never ceases to amaze me.

Well done, peeps.

Thanks that was very helpful, will dig thru your link...