Lecture 2 - Norms

Question 1

What is the raw score?

Answer 1

The score of an individual on a test - not meaningful, not going to know whether good/bad score

Question 2

What are derived scores?

Answer 2

Allows us to ascertain an individual’s position relative to a standardisation (or normative) sample i.e. by reference to norms

Question 3

What are the three types of derived scores?

Answer 3

1. percentiles
2. standard
3. age scores

Question 4

What is a percentile score & what is it represented by?

Answer 4

(P) - percentage of people in the standardisation sample who fall below a particular raw scores

Question 5

What are the advantages of a percentile score?

Answer 5

easy to compute, readily understood, univeral

Question 6

What are the disadvantages of a percentile score?

Answer 6

inequality of units at the extremes of the distribution - space between the points on a percentile scale is not the same as a space between raw scores

Question 7

What is a standard score & what is it represented by?

Answer 7

linear z - express an individual’s score in terms of the distance from the mean. That distance is measured in standard deviation units.

Question 8

In a linear z or z score formula, what does x mean?

Answer 8

z= (x) individuals test score minus (-) the (M) mean from the standardisation sample divided by (/) (s) the standard deviation for the standardisation sample

Question 9

Why is linear z nice statistically?

Answer 9

retains the exact numerical relationship btw raw scores because we’ve subtracted by a constant and divided by a constant. So the distance between individuals is retained in the z score distribution.

Question 10

What is the normal distribution range for z?

Answer 10

-3 to +3

Question 11

What is the relationship between a z score and a percentile score?

Answer 11

if you had a z score of 2 (look at the SD numbers below the bell curve) it would correlate to a percentile score just below it (97.7%)

Question 12

How do you get the T score (transformation of Linear z)?

Answer 12

Z x 10 + 50

Question 13

When are T scores commonly used?

Answer 13

personality testing

Question 14

Linear standard scores will be comparable only if?

Answer 14

They come from similar distributions

Question 15

What is the deviation IQ score?

Answer 15

to ensure comparability of IQ scores

Question 16

How do you find the deviation IQ score?

Answer 16

z + mean of standard score + standard deviation

Question 17

A test score (x) is made up of what two things?

Answer 17

true score (t) + errors (e)

Question 18

What do confidence errors do?

Answer 18

We put them around an obtained score to aid in its interpretation

Question 19

What is the formula for a 95% confidence interval?

Answer 19

score (x) is equal to plus or minus 1.96 x standard devation

Question 20

What is the formula for test scores re 95% confidence interval?

Answer 20

true score (x) is equal to plus or minus 1.96 X the standard error of measurement

Question 21

What is the assumption of true score theory?

Answer 21

If you gave the same test to someone an infinite number of times, the scores because of error in measurement, would fall out in a normal curve.

Question 22

In true score theory, the mean of the normal curve is equal to

Answer 22

true score

Question 23

In true score theory, the SD of the normal curve is equal to

Answer 23

standard error of measurement

Question 24

What do we use the reliability coefficient for?

Answer 24

estimate the parameters that we need in order to find a 95% confidence interval

Question 25

What does a z score of 0 mean?

Answer 25

the score is at the mean

Question 26

What does a z score of -1 mean?

Answer 26

score is one point below the mean

Question 27

What does a z score of +1 mean?

Answer 27

score is one point above the mean