AP Statistics Flashcards

AP Statistics vocabulary.

6931516	context	ideally tells who was measured, what was measured, how the data were collected, where the data were collected, and when and why the study was performed	0
6931517	data	systematically recorded information, whether numbers or labels, together with its context	1
6931518	data table	an arrangement of data in which each row represents a case and each column represents a variable	2
6931519	case	an individual about whom or which we have data	3
6931520	variable	holds information about the same characteristic for many cases	4
6931521	categorical variable	a variable that names categories (whether with words or numerals)	5
6931522	quantitative variable	a variable in which the numbers act as numerical values; always has units	6
6931523	units	a quantity or amount adopted as a standard of measurement, such as dollars, hours, or grams	7
6931524	frequency table	lists the categories in a categorical variable and gives the count or percentage of observations for each category	8
6931525	distribution	gives the possible values of the variable and the relative frequency of each value	9
6931526	area principle	in a statistical display, each data value should be represented by the same amount of area	10
6931527	bar chart	shows a bar representing the count of each category in a categorical variable	11
6931528	pie chart	shows how a "whole" divides into categories by showing a wedge of a circle whose area corresponds to the proportion in each category	12
6931529	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	13
6931530	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	14
6931531	conditional distribution	the distribution of a variable restricting the who to consider only a smaller group of individuals	15
6931532	independence	variables are said to be this if the conditional distribution of one variable is the same for each category of the other	16
6931533	simpson's paradox	when averages are taken across different groups, they can appear to contradict the overall averages	17
6931534	distribution	gives the possible values of the variable and the frequency or relative frequency of each value	18
6931535	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	19
6931536	stem-and-leaf display	shows quantitative data values in a way that sketches the distribution of the data	20
6931537	dotplot	graphs a dot for each case against a single axis	21
6931538	shape	to describe this aspect of a distribution, look for single vs. multiple modes, and symmetry vs. skewness	22
6931539	center	a value that attempts the impossible by summarizing the entire distribution with a single number, a "typical" value	23
6931540	spread	a numerical summary of how tightly the values are clustered around the "center"	24
6931541	mode	a hump or local high point in the shape of the distribution of a variable; the apparent locations of these can change as the scale of a histogram is changed	25
6931542	unimodal	having one mode; this is a useful term for describing the shape of a histogram when it's generally mound-shaped	26
6931543	bimodal	distributions with two modes	27
6931544	multimodal	distributions with more than two modes	28
6931545	uniform	a distribution that's roughly flat	29
6931546	symmetric	a distribution is this if the two halves on either side of the center look approximately like mirror images of each other	30
6931547	tails	the parts of a distribution that typically trail off on either side; they can be characterized as long or short	31
6931548	skewed	a distribution is this if it's not symmetric and one tail stretches out farther than the other	32
6931549	outliers	extreme values that don't appear to belong with the rest of the data	33
6931550	timeplot	displays data that change over time	34
6931551	center	summarized with the mean or the median	35
6931552	median	the middle value with half of the data above and half below it	36
6931553	spread	summarized with the standard deviation, interquartile range, and range	37
6931554	range	the difference between the lowest and highest values in a data set	38
6931555	quartile	the lower of this is the value with a quarter of the data below it; the upper of this has a quarter of the data above it	39
6931556	interquartile range	the difference between the first and third quartiles	40
6931557	percentile	the ith ___ is the number that falls above i% of the data	41
6931558	5-number summary	consists of the minimum and maximum, the quartiles Q1 and Q3, and the median	42
6931559	boxplot	displays the 5-number summary as a central box with whiskers that extend to the non-outlying data values	43
6931560	mean	found by summing all the data values and dividing by the count	44
6931561	variance	the sum of squared deviations from the mean, divided by the count minus one	45
6931562	standard deviation	the square root of the variance	46
6931563	comparing distributions	when doing this, consider their shape, center, and spread	47
6931564	shifting	adding a constant to each data value adds the same constant to the mean, the median, and the quartiles, but does not change the standard deviation or IQR	48
6931565	rescaling	multiplying each data value by a constant multiplies both the measures of position and the measures of spread by that constant	49
6931566	standardizing	done to eliminate units; values can be compared and combined even if the original variables had different units and magnitudes	50
6931567	standardized value	value found by subtracting the mean and dividing by the standard deviation	51
6931568	normal model	useful family of models for unimodal, symmetric distributions	52
6931569	parameter	numerically valued attribute of a model	53
6931570	statistic	value calculated from data to summarize aspects of the data	54
6931571	z-score	tells how many standard deviations a value is from the mean; have a mean of zero and a standard deviation of one	55
6931572	standard normal model	a normal model with a mean of 0 and a standard deviation of 1	56
6931573	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	57
6931574	normal percentile	this corresponding to a z-score gives the percentage of values in a standard normal distribution found at that z-score or below	58
6931575	normal probability plot	a display to help assess whether a distribution of data is approximately normal; if it is nearly straight, the data satisfy the nearly normal condition	59
6931576	changing center and spread	doing this is equivalent to changing its units	60
6933787	scatterplots	shows the relationship between two quantitative variables measured on the same cases	61
6933788	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	62
6933789	form	the ____ we care about most is straight	63
6933790	strength	a scatterplot shows an association that is this if there is little scatter around the underlying relationship	64
6933791	correlation	a numerical measure of the direction and strength of a linear association	65
6933792	outlier	a point that does not fit the overall pattern seen in the scatterplot	66
6933793	lurking variable	a variable other than x and y that simultaneously affects both variables, accounting for the correlation between the two	67
6933794	model	an equation or formula that simplifies and represents reality	68
6933795	linear model	an equation of the form y-hat = b0 + b1x	69
6933796	residuals	the differences between data values and the corresponding values predicted by the regression model; ____ = observed value - predicted value	70
6933797	predicted value	found by substituting the x-value in the regression equation; they're the values on the fitted line	71
6933798	slope	gives a value in "y-units per x-unit"; changes of one unit in x are associated with changes of b1 units in predicted values of y	72
6933799	regression to the mean	each predicted y-hat tends to be fewer standard deviations from its mean than its corresponding x was from its mean	73
6933800	regression line	the linear equation y-hat = b0 + b1x that satisfies the least squares criterion	74
6933801	intercept	this, b0, gives a starting value in y-units; it's the y-hat-value when x is 0	75
6933802	least squares	this criterion specifies the unique line that minimizes the variance of the residuals or, equivalently, the sum of the squared residuals	76
6933803	r2	the square of the correlation between y and x; gives the fraction of the variability of y accounted for by the least squares linear regression on x; an overall measure of how successful the regression is in linearly relating y to x	77
6933804	subset	if data consist of two or more groups that have been thrown together, it is usually best to fit different linear models to each group than to try to fit a single model to all of the data	78
6933805	extrapolation	although linear models provide an easy way to predict values of y for a given value of x, it is unsafe to predict for values of x far from the ones used to find the linear model equation; predictions should not be trusted	79
6933806	outlier	any data point that stands away from the others; can be extraordinary by having a large residual or by having high leverage	80
6933807	leverage	data points whose x-values are far from the mean of x are said to exert ____ on a linear model; with high enough ____, residuals can appear to be deceptively small	81
6933808	influential point	when omitting a point from the data results in a very different regression model, the point is an ____	82
6933809	lurking variable	a variable that is not explicitly part of a model but affects the way the variables in the model appear to be related	83
6933810	re-express data	we do this by taking the logarithm, the square root, the reciprocal, or some other mathematical operation on all values in the data set	84
6933811	ladder of powers	places in order the effects that many re-expressions have on the data	85
6934222	random	an event is this if we know what outcomes could happen, but not which particular values will happen	86
6934223	random numbers	these are hard to generate, but several websites offer an unlimited supply of equally likely random values	87
6934224	simulation	models random events by using random numbers to specify event outcomes with relative frequencies that correspond to the true real-world relative frequencies we are trying to model	88
6934225	simulation component	the most basic situation in a simulation in which something happens at random	89
6934226	outcome	an individual result of a component of a simulation	90
6934227	trial	the sequence of several components representing events that we are pretending will take place	91
6934228	response variable	values of this record the results of each trial with respect to what we were interested in	92
6934229	population	the entire group of individuals or instances about whom we hope to learn	93
6934230	sample	a representative subset of a population, examined in hope of learning about the population	94
6934231	sample survey	a study that asks questions of a sample drawn from some population in the hope of learning something about the entire population	95
6934232	bias	any systematic failure of a sampling method to represent its population; common errors are voluntary response, undercoverage, nonresponse ____, and response ____	96
6934233	randomization	the best defense against bias, in which each individual is given a fair, random chance of selection	97
6934234	matching	any attempt to force a sample to resemble specified attributes of the population	98
6934235	sample size	the number of individuals in a sample	99
6934236	census	a sample that consists of the entire population	100
6934237	population parameter	a numerically valued attribute of a model for a population	101
6934238	representative	a sample is this if the statistics computed from it accurately reflect the corresponding population parameters	102
6934239	simple random sample	this of sample size n is one in which each set of n elements in the population has an equal chance of selection	103
6934240	sampling frame	a list of individuals from whom the sample is drawn	104
6934241	sampling variability	the natural tendency of randomly drawn samples to differ	105
6934242	stratified random sample	a sampling design in which the population is divided into several subpopulations, and random samples are then drawn from each stratum	106
6934243	cluster sample	a sampling design in which entire groups are chosen at random	107
6934244	multistage sample	sampling schemes that combine several sampling methods	108
6934245	systematic sample	a sample drawn by selecting individuals systematically from a sampling frame	109
6934246	voluntary response bias	bias introduced to a sample when individuals can choose on their own whether to participate in the sample	110
6934247	convenience sample	consists of the individuals who are conveniently available	111
6934248	undercoverage	a sampling scheme that biases the sample in a way that gives a part of the population less representation than it has in the population	112
6934249	nonresponse bias	bias introduced to a sample when a large fraction of those sampled fails to respond	113
6934250	response bias	anything in a survey design that influences response	114
6940717	observational study	a study based on data in which no manipulation of factors has been employed	115
6940718	retrospective study	an observational study in which subjects are selected and then their previous conditions or behaviors are determined	116
6940719	prospective study	an observational study in which subjects are followed to observe future outcomes	117
6940720	experiment	manipulates factor levels to create treatments, randomly assigns subjects to these treatment levels, and then compares the responses of the subject groups across treatment levels	118
6940721	random assignment	to be valid, an experiment must assign experimental units to treatment groups at random	119
6940722	factor	a variable whose levels are controlled by the experimenter	120
6940723	response	a variable whose values are compared across different treatments	121
6940724	experimental units	individuals on whom an experiment is performed	122
6940725	level	the specific values that the experimenter chooses for a factor	123
6940726	treatment	the process, intervention, or other controlled circumstance applied to randomly assigned experimental units	124
6940727	principles of experimental design	control, randomize, replicate, block	125
6940728	statistically significant	when an observed difference is too large for us to believe that is is likely to have occurred naturally	126
6940729	control group	the experimental units assigned to a baseline treatment level, typically either the default treatment, which is well understood, or a null, placebo treatment	127
6940730	blinding	any individual associated with an experiment who is not aware of how subjects have been allocated to treatment groups	128
6940731	single-blind	when either those who could influence or evaluate the results is blinded	129
6940732	double-blind	when both those who could influence and evaluate the results are blinded	130
6940733	placebo	a treatment known to have no effect, administered so that all groups experience the same conditions	131
6940734	placebo effect	the tendency of many human subjects (often 20% or more of experiment subjects) to show a response even when administered a placebo	132
6940735	block	when groups of experimental units are similar, it is a good idea to gather them together into these	133
6940736	matched	in a retrospective or prospective study, subjects who are similar in ways not under study may be ____ and then compared with each other on the variables of interest	134
6940737	randomized block design	randomization occurring within blocks	135
6940738	completely randomized design	all experimental units have an equal chance of receiving any treatment	136
6940739	confounded	when the levels of one factor are associated with the levels of another factor so their effects cannot be separated	137