Variability

Question 1

Variability

Answer 1

The degree of differences within a set of test scores or among the values of a psychological attribute. Mostly indexed with standard deviation and variance

Question 2

Variance

Answer 2

Checking the deviation of the score from the mean.
(X - X-bar).

Then each deviation is squared to get the squared deviation (all added up forms sum of squares).

Then the mean of the squared deviation is calculated (dividing sum of squares with N), resulting in the variance (s2)

Question 3

Standard deviation

Answer 3

Square root of the variance. It reflects the variability in terms of size of raw scores.

Question 4

4 factors to consider the nature of variance and sd

Answer 4

1. It can never be less than 0
2. There is no simple way to interpret how large/small they are
3. they’re most interpretable if put in context, eg outcome of other test w same measures.
4. The importance lies mainly on their effects on other values that are more directly interpretable.