Chapter 2

Question 1

Inferences:

Answer 1

Logical deductions about events that can’t be observed directly.

Question 2

Descriptive Statistics

Answer 2

Methods used to provide a concise description of a collection of quantitative information.

Question 3

Inferential Statistics:

Answer 3

Methods used to make inferences from a small group of people, known as a sample, to a large group of people, known as a population.

Question 4

Psychological Testing

Answer 4

based on Inferential Statistics.

Question 5

Measurement:

Answer 5

The application of rules for assigning numbers to objects.

Question 6

-Magnitude: (scale)

Answer 6

-Magnitude: “moreness” (such as “taller,” “shorter”

Question 7

-Equal Intervals:(scale)

Answer 7

: The difference between two points next to each other is the same (such as inches)

Question 8

-Absolute 0: (scale)

Answer 8

It is possible to have none of a particular quality being measured (a heart rate of 0 means the patient is dead)

Question 9

*Nominal Scales (type of scale)

Answer 9

Not really scales, just assigning random designator numbers to people or things (football jerseys)
-no properties of of a numbered scale

Question 10

*Ordinal Scales:(type of scale)

Answer 10

Have the property of “moreness” but not equal intervals or absolute 0 (like “taller”)

Question 11

*Interval Scales:(type of scale)

Answer 11

Have magnitude and equal intervals, but not necessarily absolute 0–temperature in ºF or ºC, for example

Question 12

*Ratio Scales: (type of scale)

Answer 12

Have magnitude, equal intervals and absolute 0

Question 13

*frequency distribution

Answer 13

summarizes the scores of a group of individuals in terms of how frequently each value was obtained (horizontal axis from lowest to highest)

Question 14

bell-shaped curve

Answer 14

with a mean where the median and the mode are. If it’s skewed, the median isn’t at the mode

Question 15

positive skew

Answer 15

means more scores are above the mode than below it

Question 16

negative skew

Answer 16

means more scores are below the mode than above it

Question 17

class interval

Answer 17

the distance between two consecutive measurements. This is a value that you decide is the meaningful difference between one measurement and the next higher one.
Examples: Temperature, money, length (metric or British)

Question 18

Percentile Ranks:

Answer 18

A percentile rank answers the question “what percent of the scores fall below a particular score (X1)?”

Question 19

Importance of percentile rank

Answer 19

because that is the information that an IQ score gives you—that is, how your intelligence score compares to that of other people; where you are in the total distribution of IQ scores. Deviation IQ is based on this

Question 20

Percentiles

Answer 20

are the specific scores or points within a distribution. They divide the total frequency for a set of observations into hundredths

Question 21

Difference between percentile and percentile rank

Answer 21

Percentile is a measure of relative performance–you must specify the population to which the score in question is being compared

Question 22

*Mean:

Answer 22

The average score in a distribution

The mean = the sum of all scores divided by the number of cases.

Question 23

Median:

Answer 23

The point where half the cases are above it and half below

Question 24

Mode:

Answer 24

The “bump,” the point where the largest number of cases fall

Question 25

*Standard Deviation:

Answer 25

An approximation of the average deviation around the mean.

Question 26

*Variance:

Answer 26

The variation of the scores around the mean; calculated as the squared deviation around the mean.

Question 27

Variance

Answer 27

σ2 = Σ(X – X)2
N
(Variance is easier to calculate, but SD (or σ) is more meaningful, more important)

Question 28

σ

Answer 28

refers to the standard deviation of a population

Question 29

S

Answer 29

refers to the standard deviation of a sample drawn from that population.

Question 30

sample from population

Answer 30

A subset of the population, drawn to represent it in an unbiased (random) fashion

Question 31

Z-scores

Answer 31

indicate a score’s percentile rank in terms of the standard deviation of the distribution

Question 32

Z =

Answer 32

distance of a score from the mean in standard deviations, with scores above the mean stated as positive Z-scores and scores below the mean stated as negative Z-scores

Question 33

A Z score of 1.0 means the person’s score

Answer 33

approximately the 84th percentile.

Question 34

A Z score of -1.0 is at

Answer 34

approximately the 16th percentile.

Question 35

Wechsler IQ Tests

Answer 35

the most commonly used individual IQ tests, have been defined to have a Standard Deviation of 15 because that was closest to the Standard Deviation of the scores on the Stanford-Binet, calculated by the formula of Mental Age ÷ Chronological Age X 100.

Question 36

deviation IQ score

Answer 36

The score tells you where you are in the distribution of other individuals your age

Question 37

standard normal distribution

Answer 37

(the “bell-shaped curve”) is also called the symmetrical binomial probability distribution

Question 38

Units on the X (horizontal) axis are

Answer 38

usually given in Z units

Question 39

McCall’s T

Answer 39

In 1939 W.A. McCall developed a system in which scores on standardized exams were presented as standard deviations, where instead of a standard deviation being equal to 1, as it is with Z-scores, it’s equal to 10.
He set the mean at 50 rather than at zero, so that one standard deviation below the mean is 40, and one standard deviation above the mean is 60.

Question 40

who uses mccall’s T system

Answer 40

MMPI scaled scores are still graphed using this system. SAT and GRE scores are the same except that μ = 500 and Z=100.

Question 41

how can you get tscores

Answer 41

applying the formula T = 10Z + 50 (and you can calculate back the other way if you want to).

Question 42

Quartile systems

Answer 42

divided the percentage scale into four groups (“You’re in the top quarter of…”)

Question 43

decile systems

Answer 43

divide the scale into tenths.

Question 44

“interquartile range”

Answer 44

is the middle 50% of scores

Stanines divide the scores into “standard 9ths”

Question 45

*Norm-referenced tests

Answer 45

compare individuals to a normative group (and therefore if you can make somebody else look worse, you look better).

Question 46

*Criterion-referenced tests

Answer 46

compare an individual to a criterion on specific types of skills, tasks, or knowledge (so making somebody else look bad doesn’t help you.)