Definitions

Question 1

variable whose values are numbers, also called a quantitative variable

Answer 1

numeric variable

Question 2

variable in which the numbers stand for approximately equal amounts of what is being measured

Answer 2

equal-interval variable

Question 3

ratio scale

Answer 3

an equal-interval variable is measured on a ratio scale if it has an absolute zero point, meaning that the value of zero on the variable indicates a complete absence of the variable.

Question 4

numeric variable in which the values are ranks, such as class standing or place finished in a race. Also called ordinal variable

Answer 4

rank-order variable

Question 5

variable that has specific values and that cannot have values between these specific values.

Answer 5

discrete variable

Question 6

variable for which, in theory, there are an infinite number of values between any two values.

Answer 6

continuous variable

Question 7

typical or most representative value of a group of scores

Answer 7

central tendency

Question 8

Σ

Answer 8

sum of

Question 9

measure of how spread out a set of scores are; average of the squared deviations from the mean.

Answer 9

variance

Question 10

score minus the mean

Answer 10

deviation score

Question 11

square of the difference between a score and the mean.

Answer 11

squared deviation score

Question 12

total of each score’s squared difference from the mean

Answer 12

sum of squared deviations

Question 13

square root of the average of the squared deviations from the mean; approximately the average amount that scores in a distribution vary from the mean.

Answer 13

standard deviation

Question 14

Z Score

Answer 14

raw score, minus the mean, divided by the standard deviation

Question 15

number of successful outcomes divided by the number of total outcomes you would expect to get if you repeated an experiment a large number of times.

Answer 15

expected relative frequency

Question 16

roughly speaking, the range of scores (that is, the scores between an upper and lower value) that is likely to include the true population mean; more precisely, the range of possible population means from which it is not highly unlikely that you could have obtained your sample mean.

Answer 16

confidence interval

Question 17

incorrect conclusions in hypothesis testing in relation to the real (but unknown) situation, such as deciding the null hypothesis is false when it is really true.

Answer 17

decision errors

Question 18

rejecting the null hypothesis when in fact it is true; getting a statistically significant result when in fact the research hypothesis is not true.

Answer 18

type I error

Question 19

failing to reject the null hypothesis when in fact it is false; failing to get a statistically significant result when in fact the research hypothesis is true.

Answer 19

type II error

Question 20

standardized measure of difference (lack of overlap) between populations, increases with greater differences between means.

Answer 20

effect size

Question 21

d

Answer 21

effect size symbol

Question 22

statistical method for combining effect sizes from different studies.

Answer 22

meta-analysis

Question 23

probability that the study will give a significant result if the research hypothesis is true.

Answer 23

statistical power

Question 24

your sample’s mean minus the population mean, divided by the standard deviation of the distribution of means.

Answer 24

t score

Question 25

extent to which a particular hypothesis-testing procedure is reasonably accurate even when its assumptions are violated.

Answer 25

robustness

Question 26

hypothesis-testing procedure in which there are two separate groups of people tested and in which the population variance is not known.

Answer 26

t test for independent means

Question 27

S^2 Pooled in a t test for independent means, weighted average of the estimates of the population variance from two samples (each estimate weighted by the proportion consisting of its sample’s degrees of freedom divided by the total degrees of freedom for both samples).

Answer 27

pooled estimate of the population variance

Question 28

ratio of the between-groups population variance estimate to the within-groups population variance estimate.

Answer 28

F Ratio

Question 29

relation between two variables in which high scores on one go with high scores on the other, mediums with mediums, and lows with lows; on a scatter diagram, the dots roughly follow a straight line sloping up and to the right.

Answer 29

positive correlation

Question 30

relation between two variables in which high scores on one go with low scores on the other, mediums with mediums, and lows with highs; on a scatter diagram, the dots roughly follow a straight line sloping down and to the right.

Answer 30

negative correlation

Question 31

the result of multiplying a person’s Z score on one variable by the person’s Z score on another variable.

Answer 31

cross product of Z scores

Question 32

correlation coefficient

Answer 32

The correlation coefficient is the sum, over all the people in the study, of the product of each person’s two Z scores, then divided by the number of people.

Question 33

in a linear prediction rule, particular fixed number added into the prediction.

Answer 33

regression constant (a)

Question 34

number multiplied by a person’s score on a predictor variable as part of a linear prediction rule.

Answer 34

regression coefficient (b)

Question 35

steepness of the angle of a regression line in a graph of the relation of scores on a predictor variable and predicted scores on a criterion variable; number of units the line goes up for every unit it goes across.

Answer 35

slope

Question 36

the point where the regression line crosses the vertical axis; the regression constant (a).

Answer 36

intercept

Question 37

in prediction, the difference between a person’s predicted score on the criterion variable and the person’s actual score on the criterion variable.

Answer 37

error