# AP Statistics 4 Flashcards

Terms Definitions
 Interquartile Range - resistant? Resistant Variable Any Characteristic of an individual. Roundoff error Residuals from least-squares regression have a special property: the mean of the residuals is always zero. The sum in -0.0002 in the calculator because the software rounded to 4 decimal places. parameter numerically valued attribute of a model blocking subjects or experimental units are grouped together homogeneously because of some charcteristic they have in common that is believed might effect the experiment Percentile An observation's percentile is the percent of the distribution that is at or to the left of the observation. 4 Significance level Anoter name for alpha level marginal distribution the distribution of either variable alone in a contingency table; the counts or percentages are the totals found in the margins (last row or column) of the table correlation a numerical measure of the direction and strength of a linear association resistant values that are not strongly affected by extreme values, the median is more resistant that the mean. The standard deviation is most strongly affected by extreme values explanatory variable the independent variable that attempts to explain the relationship with the other variable. It becomes the x variable on the graph five-number summary the smallest and largest observations, the first and third quartiles, and the median bar chart chart used for categorical data; categorical variables on x-axis; bars are NOT connected Standard deviation s = √[(1/(n-1))∑(x₁ - ¯x¯)²] Use for normal distributions. Conditional Distributions To find the conditional distribution of the row variable for one specific value of the column variable, look only at that one column in the table. Find each entry in the column as a percent of the column total.There is a conditional distribution of the row variable for each column in the table. Comparing these conditional distributions is one way of showing the association between the row and the collumn variables. Compare the conditional distributions of the row variable for the different categories of the column variable when you think of the collun variable as the esplanatory variable. If the row variable is your explanatory variable, look at each row separately and show the association by comparing the conditional distributions of the column variable in the rows. 1 Marinal Distribution In a contingency table, the distribution of either variable one Double-blind In which neither the subjects nor the individuals who measure the response know which treatment was received. form the ____ we care about most is straight sample size the number of individuals in a sample left skewed distribution a distribution that has a concentration of data on the upper end and the tail on the left outlier a point that lies outside the overall pattern of the data Z score The number of standard deviations a value is from the mean of its distribution standard normal distribution the Normal distribution N(0,1) with mean 0 and standard deviation 1 Residual plot Plots the residents on the vertical axis against the explanatory variable on the horizontal axis. Magnifies the residuals and makes patterns easier to see. 4 Mutually exclusive When two events share no common outcomes Simple Random Sample A sample in which every possible sample of the same size has the same chance of being selected. voluntary response bias bias introduced to a sample when individuals can choose on their own whether to participate in the sample control group a group created the provide a basis for comparison usually either an old or placebo treatment variances s^2 the average of the squares of the deviations of the observations from their mean undercoverage when a group is left out of the process of choosing the sample Lurking variable A lurking variable is a variable that has an important effect on the relationship among the variables in a study but is not included among the variables studied. 1 Outliers any value that is more than 1.5 (IQR) from either end of a box plot. A point that does not fit. 68-95-99.7 rule in a normal model, about 68% of values fall within 1 standard deviation of the mean, about 95% fall within 2 standard deviations of the mean, and about 99.7% fall within 3 standard deviations of the mean Sum of the probabilities of a distribution must add to one Split stems Double each stem on a stemplot (0-4 on the first stem, 5-9 on the second stem). 4 Binomial probability model Counts the number of successes in n trials distribution skewed to the right the right side of the histogram extends much farther than the left side A or B, A U B the event consisting of all outcomes in at least one of the two events The Standard Normal Table Table A is a table of areas under the SNC. The table entry for each value z is the area under the curve to the left of z.
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