Math1041, calculating variance (1 Viewer)

[Tim035]

I've got a tute test on monday, and going over the practice papers I've gotten stuck on this question where it's asking you to calculate variance.
But its only given you the variables and their respective probabilities, it has not given you the number of observations.
How do you calculate variance if you don't know 'n' ?

 

[ace]

That's scenario analysis then;

variance = sum of ((r - E(r))^2)*pi

where;
pi = probabilitiy of occurence of ith state of nature
r = return in ith state of nature
E(r) = average of r; expectation of r; etc. (might be represented by r', etc.)

I'm guessing you've only seen time series, where the number of observations is needed.