Standard deviation, mean, etc?

Question 1

Σ

Answer 1

the sum of

Question 2

mean

Answer 2

x̄= Σχ/n

Question 3

Σ(x-x̄)^2

Answer 3

this is called Sχχ

Question 4

Easier way to write Sχχ

Answer 4

Σχ^2-nx̄^2

Question 5

Standard deviation

Answer 5

σχ= √(Σ(x-x̄)^2)/(n-1)
=√(Sχχ)/(n-1)
=√(Σχ^2-nx̄^2)/(n-1)
Just so you know, on calc is called sχ for no reason