Psychological Statistics

Question 1

Nominal Scale of Measurement

Answer 1

Name different categories
No quantitative properties
Numbers are just used as names

Question 2

Ordinal Scale of Measurement

Answer 2

Numbers differentiate categories or instances
Numbers convey an ordered series of relationship
Can’t assume equal increments (1 to 2)
Example? Ranks

Question 3

Interval Scale of Measurement

Answer 3

Has all properties of nominal and ordinal
A numerical difference means the same thing across the scale
Zero does not mean absence of thing measured
Example? degrees F, C, or

Question 4

Ratio Scale of Measurement

Answer 4

Has all properties of nominal, ordinal, and interval
Zero point is absolute
Example? time, degrees K

Question 5

discontinuous (discrete) variable

Answer 5

Variable for which only a finite number of values can occur between any two points
E.g. 1 person or 3 persons not 1.5 person or 2.7 person

Question 6

Continuous variables

Answer 6

Theoretically can assume an infinite number of values between any two points
E.g. height, age, reaction times

Question 7

independent variable

Answer 7

the variable manipulated by the researcher

Question 8

dependent variable

Answer 8

the variable being measured by the researcher

Question 9

Real (true) limits

Answer 9

applied to a continuous variable and it is (+/-) one half of the unit measured (decimal place). E.g.
47 + .5= 47.5
47 - .5= 46.5
or 47.5 + .05= 47.55
47.5 - .05= 47.45

Question 10

Rounding Conventions

Answer 10

Round to two decimal places
Greater than 5 round up
Less than 5 leave unchanged
Exactly 5 round up to nearest even digit if not already there
6.575 –> 6.58
6.525 –> 6.52

Question 11

Frequency Histogram

Question 12

frequency polygon

Question 13

Line Plot

Question 14

Mesokurtosis

Question 15

Platykurtosis

Question 16

LeptoKurtosis

Question 17

stem and leaf plot

Question 18

Frequency Distributions for Quantitative Variables: Ungrouped Scores

Answer 18

scores are arranged from highest to lowest (x)
second column indicates the frequency (f)
detailed

Question 19

Frequency Distributions for Quantitative Variables: Grouped Frequency Distribution

Answer 19

arranged from highest to lowest
specify score INTERVALS and count how many scores fall in each interval
less detailed

Question 20

mode

Answer 20

most frequent score in a data set
data set can have 2 modes making it bimodal

Question 21

median

Answer 21

middle score
if N is even (N+1)/2
take the average of adjacent scores

Question 22

mean

Answer 22

X bar for sample
mu for population

Question 23

positively skewed

Answer 23

mode - median - mean

Question 24

negatively skewed

Answer 24

mean - median - mode

Question 25

range

Answer 25

X highest - X lowest Sensitive to outliers

Question 26

interquartile range

Answer 26

difference between the 25th percentile and the 75th percentile isn't affected by outliers so much but does omit data

Question 27

standard deviation

Question 28

variance