# AP Statistics Vocabulary 2 Flashcards

Terms Definitions
 homogeneous similar in makeup standardized value z - score symmetric type of distribution shape; approximately mirror-image; no data set is perfect mirror-image Confidence Level the estimated probability parameter lies within a given range of numbers contingency table displays counts and, sometimes, percentages of individuals falling into named categories on two or more variables; categorizes the individuals on all variables at once, to reveal possible patterns in one variable that may be contingent on the category of the other trial the sequence of several components representing events that we are pretending will take place outcomes the results of a chance phenomenon 3 Experiment and experiment that manipulates factor levels to create Replication The repetition of an experiment in order to test the validity of its conclusion. histogram uses adjacent bars to show the distribution of vales in a quantitative variable; each bar represents the frequency (or relative frequency) of values falling in an interval of values direction a positive ____ or association means that, in general, as one variable increases, so does the other; when increases in one variable generally correspond to decreases in the other, the association is negative multistage sampling sampling schemes that combine several different sampling methods at different stages strata when groups of experimental units are similar, they are gathered into these groups µ The average of the population of data Chebyshev's inequality the percent of observations falling within k standard deviations of the mean is at least (100)(1- (1/k^2)) Normal distributions Normal distributions are described by a special family of bell-shapes symmetric density curves, called normal curves. The mean μ and standard deviation σ completely specify a normal distribution N (μ, σ). The mean is the center of the curve and σ is the distance from μ to the inflection points on either side. 3 Retrospective study An observational study where subjects are selected and their previous conditions are determined Statistically significant a term used to describe research results when the outcome of a statistical test indicates that the probability of those results occurring by chance is small variance the sum of squared deviations from the mean, divided by the count minus one confounding when the results of an experiment can be determined because a variable has not be accounted for and has interferred with your results sampling variability the natural tendency of randomly drawn samples to differ, one from another right skewed type of distribution shape; right tail is longer than left Density curve Describes the overall pattern of a distribution. Total area = 1. Area beneath curve gives proportions of observations. Probability Sample A probability sample gives each member of the population a known chance (greater than zero) to be selected. 3 Confounding Wen the levels of one factor are associated with the levels of another factor in such a way that their effects cannot be separated percentile the ith ___ is the number that falls above i% of the data Interquartile Range (IQR) the third quartile minus the first quartile matched pairs type of study in which subjects who are similar in ways not under study may be grouped together and then compared with each other on the variables of interest positively associated when above average values of one tend to accompany above the average value of others and below also tend to come together 3 Convenience sample When a sample is created by subjects that are convenient Sampling without Replacement Selecting an item and not returning it to group before re-sampling. third quartile the value where 75% of the data falls below it in an ordered list ^p; sample proportion The number of successes divided by the number of trials (n) Facts about probability 1. Any probability is a number between 0 and 1. 2. All possible outcomes together must have probability 1. 3. The probability that an event does not occur is 1 minus the probability that the event does occur. 4. If two events have no outcome in common, the probability that one or the other occurs is the sum of their individual probabilities. A and B, A /\ B the event consisting of outcomes common to both events Outlier 1.5 x IQR below Q1 or 1.5 x IQR above Q3. Mathematical model (model) The LSRL is a model for the data. If the data seems to show a linear trend, then it would be appropriate to try and fit an LSRL to the data.
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