Chapter 3 - Properties of Distributions

Question 1

Central tendency

Answer 1

Number typical of the scores in a distribution

Question 2

Dispersion

Answer 2

How spread out scores are in a distribution of a quantitative variable

Question 3

Outliers

Answer 3

Scores the deviate by an unusual amount from the central tendency of a distribution

Question 4

Range

Answer 4

Difference between largest and smallest scores in a set

Question 5

Variance

Answer 5

Mean squared deviation from the mean

Question 6

Deviation score

Answer 6

Difference between a score and the mean of the sample or pop from which it came

Question 7

Sum of squares

Answer 7

Sum of all squared deviation scores in a sample or population

Question 8

Sample variance

Answer 8

Sum of squares divided by n-1

Question 9

Standard deviation

Answer 9

Square root of the variance. Roughly the average distance of scores from the mean

Question 10

Shape of distribution

Answer 10

How density or frequency changes as a function of the values of the variable

Question 11

Normal distribution
Skewed distribution
Multimodal distribution

Answer 11

1. A unimodal, symmetrical distribution whose cross-section resembles cross-section of a bell. Bell curve
2. Asymmetrical distribution.
   Right skewed or positively
   Left skewed or negatively
3. More than one peak

Question 12

Kurtosis

Answer 12

Sharpness of a peak

Question 13

Mean

Answer 13

Balance point of a distribution
Changing the score changes the mean
Adding or subtracting a constant from each score, the same constant will be added/subtracted from the mean
Multiplying each score by a constant will change the mean the same way
To compute a grand mean, weight the two means by respective n
(n1m1)+(n2m2)/n1+n2
Used with interval, ratio

Question 14

Median

Answer 14

Not affected by extreme scores
Only appropriate measure of CT for nominal variables 
Good for skewed distributions
Not sensitive to outliers
Good when data are ordinal
Used with ordinal, interval, ratio

Question 15

Mode

Answer 15

Good for nominal data

Used with nominal, ordinal, interval, ratio

Question 16

1. CT in right skewed (positively)

2. CT in left skewed (negatively)

Answer 16

1. (Left to right): mode median mean
   Floor effect
2. (Left to right): mean median mode
   Ceiling effect