Definitions Flashcards
variable whose values are numbers, also called a quantitative variable
numeric variable
variable in which the numbers stand for approximately equal amounts of what is being measured
equal-interval variable
ratio scale
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.
numeric variable in which the values are ranks, such as class standing or place finished in a race. Also called ordinal variable
rank-order variable
variable that has specific values and that cannot have values between these specific values.
discrete variable
variable for which, in theory, there are an infinite number of values between any two values.
continuous variable
typical or most representative value of a group of scores
central tendency
Σ
sum of
measure of how spread out a set of scores are; average of the squared deviations from the mean.
variance
score minus the mean
deviation score
square of the difference between a score and the mean.
squared deviation score
total of each score’s squared difference from the mean
sum of squared deviations
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.
standard deviation
Z Score
raw score, minus the mean, divided by the standard deviation
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.
expected relative frequency
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.
confidence interval
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.
decision errors
rejecting the null hypothesis when in fact it is true; getting a statistically significant result when in fact the research hypothesis is not true.
type I error
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.
type II error
standardized measure of difference (lack of overlap) between populations, increases with greater differences between means.
effect size
d
effect size symbol
statistical method for combining effect sizes from different studies.
meta-analysis
probability that the study will give a significant result if the research hypothesis is true.
statistical power
your sample’s mean minus the population mean, divided by the standard deviation of the distribution of means.
t score
extent to which a particular hypothesis-testing procedure is reasonably accurate even when its assumptions are violated.
robustness
hypothesis-testing procedure in which there are two separate groups of people tested and in which the population variance is not known.
t test for independent means
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).
pooled estimate of the population variance
ratio of the between-groups population variance estimate to the within-groups population variance estimate.
F Ratio
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.
positive correlation
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.
negative correlation
the result of multiplying a person’s Z score on one variable by the person’s Z score on another variable.
cross product of Z scores
correlation coefficient
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.
in a linear prediction rule, particular fixed number added into the prediction.
regression constant (a)
number multiplied by a person’s score on a predictor variable as part of a linear prediction rule.
regression coefficient (b)
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.
slope
the point where the regression line crosses the vertical axis; the regression constant (a).
intercept
in prediction, the difference between a person’s predicted score on the criterion variable and the person’s actual score on the criterion variable.
error
