How do you find thesize of the typical deviation of this question?

Question

X
1
7
7
9
A)1 B)2 C)3 D)6 E)7

The answer is C, but I do not know how to solve it.

I have to find the size of the typical deviation from the mean

sorry, the size of a typical deviation from the mean, for scores on X

Answer 1

I hope English is not your native language.

Anyhow, you are surely looking for the standard deviation.

First of all, the mean of 1, 7, 7, and 9 is their sum divided by 4. I.e., it is 24/4 = 6.

Second, the standard deviation is the square root of (1/4 times the sums of the squares of the differences between the values and the means).

I.e., the square root of (1/4 *((-5)^2 + 1^2 + 1^2 + 3^2).

I.e., the square root of 36/4.

And that is of course 3.

Answer 2

Typical Deviation