Mathematics GCE A level, probability and statistics 1, Representation of data.

What's the meaning of ∑(x-a). I even asked the teacher but my brain ain't satisfied with the answer. 😂

It would help to post the actual question/formula, but I presume the x is the random variable, the sum is over the number of samples n (is there a summation / subscript index i) and a is a constant.

If so, you calculate the (sample) mean, mu, of the random variable as
mu = (∑x)/n
as you should know. So if you threw a 6 sided die (x=1,2...,6) n=10 times, then the expected value of ∑x would be 35 and the mean would be 3.5. If a=1, then youre simply doing a translation of the random variable by 1 (so the die scores become 0 to 5) and in this case the expected value of
∑(x-1)
would be 25

(edited 2 months ago)