Measurement of Variability

Question 1

Refers to the spread of scores in a distribution, it refers to the amount of spread of the scores around the mean

Answer 1

Measurement of Variability

Question 2

What are the different measures of variability

Answer 2

• Range
• Interquartile
• Variance
• Standard Deviation

Question 3

The difference between the highest and lowest scores in a distribution.

Answer 3

Range (R)

Question 4

What is the formula for range?

Answer 4

R = H - L

R = range
H = highest score in a
distribution
L = lowest score in a
distribution

Question 5

Includes the middle 50% of score values in the distribution, when they are arranged in order of size.

Answer 5

Inter-quartile range (IQR)

Question 6

What is the formula for inter-quartile range

Answer 6

IQR = Q3 - Q1

where Q1 is the score value at or below which 25% of the cases fall, and Q3 is the score
value at or below which 75% of the cases fall.

Position of Q3 = .75(N+1)
Position of Q1 = .25(N+1)

Question 7

Defined as the distance and direction of any
given raw score from its mean.

Answer 7

Deviation

Question 8

The average of squared distances from the mean

Answer 8

Variance

Question 9

What is the formula for variance

Answer 9

If Sample:

s² =Σ (X-X̄) ² / n-1

If Population:

s² =Σ (X- μ) ² / n

Question 10

How to get the standard deviation?

Answer 10

Just squared root the variance