# How to calculate if a mean is above chance level

#### knut

##### New Member
Dear all,

I have a problem to compare means from two groups with chance level.
The Variable I want to compare against chance level is calculated like: X=(Var1-Var2)/(Var1+Var2).
How do I calculate chance level and how can I say if the mean I measured is significant above chance level or not?

Thank you very much for your help and sorry for my bad english...

Best,
Knut

#### rogojel

##### TS Contributor
hi,
could you give a bit more details. It seems that you sample two variables and calculate your X using the values. So, you should have set of X values, and you calculate the mean of that set, right? What is exactly the question you need ro answer?

Something like, is the real mean X larger the, ( different feom) a given value?

regards
rogojel

#### hlsmith

##### Omega Contributor
Yeah, I don't see a mean here unless you are averaging the x variable. Then what mean are you comparing it to?

Chance level in a mean comparison is typically just your cut-off for the test statistic. So if you say your level of significant (alpha) is 0.05, you just look up that cut-off level for the test statistic given the number of degrees of freedom you have in your test.

As rog said, just post the question verbatim.