Descriptive Statistics (Measures of Central Tendency and Shapes of Distribution)

Question 1

typical or most representative value of a group of scores; Mean, Median, Mode

Answer 1

Central Tendency

Question 2

arithmetic average of a group of scores; sum of the scores divided by the number of scores; the balance point of a distribution

Answer 2

Mean (M)

Question 3

μ

Answer 3

population mean

Question 4

M

Answer 4

sample mean

Question 5

an average in which each observation in the data set is assigned or multiplied by a weight before summing to a single average value

Answer 5

Weighted Mean

Question 6

Characteristics of the Mean

Answer 6

1. Changing a score in the distribution can affect the value of the mean
2. Introducing a new score or removing a score can affect the value of the mean.
3. Adding or subtracting a constant from each score will change the value of the mean.
4. Multiplying or dividing each score by a constant will change the value of the mean

Question 7

When to use the Mean?

Answer 7

1. quantitative research, especially in psychological studies
2. approximately normally distributed data
3. with equal-interval variables: (Continuous Data/Variable &
   Interval/Ratio)

Question 8

middle score when all the scores in a distribution are arranged from lowest to highest

Answer 8

Median (Mdn)

Question 9

When to use the Median?

Answer 9

1. with rank-ordered variables
2. non-normal or skewed distributions
3. when a distribution has one or more outliers
4. rarely used in psychology research

Question 10

score with an extreme (very high or very low) in relation to the other scores in the distribution.

Answer 10

outliers

Question 11

value with the greatest frequency in the distribution

Answer 11

mode

Question 12

When to use the Mode?

Answer 12

1. with categorical variables (nominal)
2. rarely used in psychology research

Question 13

frequency distribution with one value clearly having a larger frequency than any other

Answer 13

Unimodal Distribution

Question 14

frequency distribution with two approximately equal frequencies, each clearly larger than any the others

Answer 14

Bimodal Distribution

Question 15

frequency distribution with two or more high frequencies separated by a lower frequency

Answer 15

Multimodal Distribution

Question 16

frequency distribution in which all values have approximately the same frequency

Answer 16

Rectangular Distribution

Question 17

distribution in which the pattern of frequencies on the left and right side are mirror images of each other

Answer 17

Symmetrical Distribution

Question 18

distribution in which the scores pile up on one side of the middle and are spread out on the other side; distribution that is not symmetrical

Answer 18

Skewed Distribution

Question 19

the peak (highest frequency) in the distribution is on the left-hand side with tail tapering off the right

Answer 19

Positively Skewed Distribution

Question 20

a situation in which many scores pile up at the low end of a distribution (creating a skewness to the right) because it is not possible to have any lower score.

Answer 20

Floor Effect

Question 21

the peak (highest frequency) in the distribution is on the right-hand side with the tail tapering of the left

Answer 21

Negatively Skewed Distribution

Question 22

a situation in which many scores pile up at the high end of a distribution (creating a skewness to the left) because it is not possible to have a higher score.

Answer 22

Ceiling Effect

Question 23

specific, mathematically defined, bell-shaped frequency distribution that is symmetrical and unimodal; distributions observed in nature and in research commonly approximates it

Answer 23

Normal Curve

Question 24

extent to which a frequency distribution deviates from a normal curve in terms of whether its curve in the middle is more peaked or flat than the normal curve.

Answer 24

Kurtosis

Question 25

the scores are concentrated towards the mean

Answer 25

Leptokurtic

Question 26

normal curve

Answer 26

Mesokurtic

Question 27

the scores have an extremely large deviation from the mean

Answer 27

Platykurtic