Midterm 1 - Scales, distributions & norms (Ch. 2)

Question 1

What are the 3 key properties of scales?

Answer 1

• magnitude: “moreness” (when we can say one instance has more/equal/less of an attribute compared to another)
• equal intervals: diff btw 2 points at any point on scale has same meaning as diff btw any 2 other points (IQ does NOT have equal intervals, diff btw 45 and 50 means smt diff than btw 105 and 110)
• absolute zero: when nothing of property measured exists

Question 2

IQ can be considered a(n) ____ scale

Answer 2

ordinal! (has property of magnitude but not equal intervals or absolute zero)

Question 3

Which of the 3 properties does each type of scale have?
- Nominal
- Ordinal
- Interval
- Ratio

Answer 3

• Nominal: none
• Ordinal: magnitude
• Interval: magnitude, equal intervals
• Ratio: magnitude, equal intervals, absolute zero

Question 4

What type of scale is most commonly used in psychological research/testing?

Answer 4

interval (eg Likert scale)

Question 5

In a nominal scale, numbers are assigned to represent _____. Appropriate statistics for these scales are _______.

Answer 5

labels or categories of data only
frequency, mode

Question 6

In an ordinal scale, numbers are assigned to _____. The distances between numbers are _____. Appropriate statistics for these scales are _______.

Answer 6

rank-ordered data; NOT equal
frequency, mode, median, percentile, rank-order correlation

Question 7

In an interval scale, numbers are assigned to _____. The distances between numbers are _____ and there (is/is not) an absolute zero point. Appropriate statistics for these scales are _______.

Answer 7

rank-ordered data; judged to be equal; is NOT
frequency, mean, mode, median, percentile, Pearson correlation, t-test

Question 8

In a ratio scale, numbers are assigned to _____. The distances between numbers are _____ and there (is/is not) an absolute zero point. Appropriate statistics for these scales are _______.

Answer 8

rank-ordered data; equal; IS absolute 0
frequency, mean, mode, median, percentile, Pearson correlation, proportion, t-test

Question 9

What are the 3 types of norms presented in class?

Answer 9

• Developmental norms (use norm sample)
• Within-group norms (use norm sample)
• Criterion-referenced norms (no norm sample)

Question 10

For developmental norms, age-equivalent or grade-equivalent scores are assigned based on the ______ score for that chronological age or grade level

Answer 10

median raw score (using mean would assume normal distribution and no outliers)

Question 11

Within-group norms use _____

Answer 11

standard scores (z-scores)

Question 12

A percentile reflects the percentage of individuals ____

Answer 12

falling below a score (eg if you score 90th percentile, 90% of ppl scored lower than you)

Question 13

What is the formula for percentiles?

Answer 13

(nL/N) x100
nL (number of ppl w lower score)
N (number of ppl in sample)

Question 14

Z-scores tell us ______

Answer 14

how far from the mean a score is

Question 15

A the curve for a normal distribution with a larger SD would (taller/flatter) vs a smaller SD

Answer 15

flatter (smaller SD is a tall spike)

Question 16

Standard deviation is a measure of ____

Answer 16

the avg distance of scores from the mean

Question 17

what is the formula for z transformation?

Answer 17

z = (X-M)/SD
X (raw score)
M (mean)

Question 18

transformed standard scores involve a ____ transformation of z-scores.

The transformed standard score = _____ + _____

Answer 18

linear!

Bz + A

A = mean, B = SD of transformed scores

Question 19

In normal distributions, __% of scores fall below the mean.
About __% of scores fall between the mean and 1 SD.
About __% of scores fall below 1 SD below the mean.

Answer 19

50%
34%
16%

Question 20

In a normal distribution:
__% of scores fall between -/+1 SD
__% of scores fall between -/+2 SD
__% of scores fall between -/+3 SD

Answer 20

68%
95%
99.7%

Question 21

What is the percentile for a z score of 1? what about -2?

Answer 21

84th percentile; 2.5th percentile

Question 22

When standard scores are near the mean, (small/large) diffs in scores correspond to (small/large) diffs in percentile

Answer 22

small; large

Question 23

T scores have a M of __ and SD of __

Answer 23

M = 50; SD = 10

Question 24

(T/F) you can use percentiles w ordinal and nominal scales

Answer 24

FALSE ordinal but not nominal

Question 25

What are 2 disadvantages of using percentiles?

Answer 25

• magnifies diffs near men, minimizes diffs at extremes
• some common stat analyses not possible w percentiles

Question 26

What are 2 disadvantages of standard scores (z-scores)?

Answer 26

• unfamiliar to many non-specialists
• interpretation difficult when distribution not normal

Question 27

What are 2 common criticisms of within-group norms?

Answer 27

• only meaningful if norm sample is representative
• within group comparisons encourage competition

Question 28

Criterion-referenced norms evaluate scores relative to ___ rather than ____

Answer 28

a standard rather than other individuals

Question 29

WHat are 3 problems w criterion-referenced norms?

Answer 29

• hard to specifically define elements of performance
• focus is just on reaching a certain minimum standard
• absence of relative knowledge

Question 30

In clinical contexts, what is considered an elevated/atypical z-score?

Answer 30

+/-2z

Question 31

What are 3 key characteristics of a good norm sample?

Answer 31

• sufficiently large (usually more representative)
• representative of target population
• contemporary/current