Statistics Flashcards

2012583830	Standardizing	We ________ to eliminate units	0
2012583831	Standardized Value	Value found by subtracting the mean and dividing by the standard deviation.	1
2012583832	Shifting	Adding a constant to the mean, the median, and the quartiles, but does not change the standard deviation or IQR.	2
2012583833	Rescaling	Multiple each data value by a constant multiplies both the measures of position and the measures of spread by that constant.	3
2012583834	Normal Model	A useful family of models for unimodel, symmetric distributions.	4
2012583835	Parameter	A numerically valued attribute of a model.	5
2012583836	Statistic	A value calculated from data to summarize aspects of the data.	6
2012583837	Z-score	Tells how many standard deviations a value is from the mean.	7
2012583838	Boxplot	Displays the 5-number summary as a central box with whiskers that extend to the non-outlying data values.	8
2012583839	Far Outlier	If a point is more than 3.0 IQR from either end of the box in a boxplot.	9
2012583840	Comparing Distributions	Consider: shape, center, spread	10
2012583841	Comparing Boxplots	Compare Shapes; Compare Medians; Compare IQRS; Check for outliers	11
2012583842	Timeplot	Displays data that change overtime.	12
2012583843	Standard Deviation	Square Root of the Var.	13
2012583844	Variance	The sum of squared dev. from the mean, divided by the count minus 1.	14
2012583845	Resistant	A calculated summary is said to be ________ if outliers have only a small effect on it.	15
2012583846	Mean	Found by summing all the data values and dividing by the count.	16
2012583847	5 Number Summary	Reports the min., Q1, the median, Q3 and the max.	17
2012583848	Percentile	The # that falls above i% of the data.	18
2012583849	Interquartile Range (IQR)	The difference between the 1st and 3rd Quartiles.	19
2012583850	Range	The difference between the lowest and highest values in a data set. Range = Max-Mir	20
2012583851	Median	Middle value, if it is not an even #, you take the average of the 2 middle #'s.	21
2012583852	Outliers	Extreme values that don't appear to belong with the rest of the data. Any point more than 1.5 IQR from either end of the box in a Boxplot.	22
2012583853	Skewed	Distribution is _________ if it's not symmetric and 1 tail stretches out farther than the other.	23
2012583854	Tails	The parts that typically trail off on either side.	24
2012583855	Symmetric	2 Halves on either side of the center look approximately like mirror images of each other.	25
2012583856	Uniform	A distribution that's roughly flat.	26
2012583857	Unimodal	1 mode	27
2012583858	Bimodal	2 modes	28
2012583859	Multimodal	More than 2 modes	29
2012583860	Mode	A hump or local high point in the shape of the distribution of a var.	30
2012583861	Spread	A numerical summary of how tightly the values are clustered around the center. Measures: IQR, Standard Dev.	31
2012583862	Center	The place in the distribution of a variable that you'd point to if you wanted to attempt the impossible by summarizing the entire distribution with a single #. Measures: Mean, Median	32
2012583863	Shape	To describe the _____ of a distribution, look for: single vs. mult. modes; symmetry vs skewness; outliers and gaps.	33
2012583864	Dotplot	Graphs a dot for each case against a single axis.	34
2012583865	Stem and Leaf Display	Shows quantitative data values in a way that sketches the distribution of the data.	35
2012583866	Gap	A region of the distribution where there are no values.	36
2012583867	Histogram	Uses adjacent bars to show the distribution of a quantitative var.	37
2012583868	Frequency Table (Relative Frequency Table)	Lists the categories in a categorical var. and gives the count of percentages of each categories observation.	38
2012583869	Distribution	The _____________ of a var. gives: possible values of the variance; the relative frequency of each value.	39
2012583870	Area Principle	In a statistical display, each data value should be represented by the same amount of area.	40
2012583871	Bar Chart	Shows a bar whose area represents the count (or percentage) of observations for each category of a categorical variance.	41
2012583872	Pie Chart	Show how a "whole" divides into categories by showing a wedge of a circle whose area corresponds to the proportion in each category.	42
2012583873	Contingency Table	Displays counts and, sometimes, percentages of individuals falling into named categories on 2 or more var.	43
2012583874	Marginal Distribution	In a contingency table, the distribution of either var. alone.	44
2012583875	Conditional Distribution	The distribution of a var. restricting the who to consider only a smaller group of individuals.	45
2012583876	Independence	Variables are ________ if the conditional distribution of one variables is the same for each category of the other.	46
2012583877	Segmented Bar Chart	Displays the conditional distribution of a categorical var. within each category of another var.	47
2012583878	Simpson's paradox	When averages are taken across different groups, they can appear to contradict the overall averages.	48
2012583879	Context	Tells who was measured, what was measured, how the data were collected, where the data was collected, and when and why the study was performed.	49
2012583880	Data	Systematically recorded info., whether #'s or labels, together with its contact.	50
2012583881	Data Table	An arrangement of data in which each row represents a case and each column represents a variable.	51
2012583882	Case	Individual about whom or which we have data.	52
2012583883	Population	All the cases we wish we knew about.	53
2012583884	Sample	The cases we actually examine in seeking to understand the much larger population.	54
2012583885	Variable	Holds info about the same characteristic for many cases.	55
2012583886	Units	A quantity or amount adopted as a standard of measurement, such as dollars, hours, or grams.	56
2012583887	Categorical Variable	A variable that names categories (words/numbers)	57
2012583888	Quantitative Variable	A variable in which the numbers act as numerical values - always have units.	58
2027682233	Random Phenomenon	If we know what outcomes could happen, but not which particular valves will happen.	59
2027682234	Trial	A single attempt or realization of a random phenomenon.	60
2027682235	Outcome	The value measured, observed, or reported for an individual instance of that trial.	61
2027682236	Event	A collection of outcomes.	62
2027682237	Sample Space	The collection of all possible outcome values.	63
2027682238	Law of Large Numbers	States that the long run-run relative frequency of repeated independent events gets closer and closer to the true relative frequency as the number of trials increases.	64
2027682239	Independence	If one event occurs it does not change the probability thta that the other event occurs.	65
2027682240	Empirical Probability	The probability comes from the long-run relative frequency of the event's occurence.	66
2027682241	Theoretical Probability	When the probability comes from a model.	67
2027682242	Personal Probability	When the probability is subjective and represents your personal degree of belief.	68
2027682243	Observational Study	A study based on data in which no manipulation of factors has been employed.	69
2027682244	Retrospective Study	An observational study in which subjects are selected and then their previous conditions or behaviors are determined.	70
2027682245	Prospective Study	An observational study in which subjects are followed to observe future outcomes.	71
2027682246	Experiment	Manipulates factor levels to create treatments. Randomly assigns subjects to these treatment levels. Compares the responses of the subject groups across treatment levels.	72
2027682247	Factor	A variance whose levels are manipulated by the experiment.	73
2027682248	Response	A variance whose values are compared across different treatments.	74
2027682249	Experimental Units	Individuals on whom an experiment is performed.	75
2027682250	Level	The specific values that the experimenter chooses for a factor.	76
2027682251	Treatment	The process, intervention, or other controlled circumstance applied to randomly assigned experimental units.	77
2027682252	Priciples of Experimental Design	Control; Randomize; Replicate; Block	78
2027682253	Control Group	The experimental units assigned to a basseline treatment level.	79
2027682254	Placebo Effect	The tendency of many human subjects to show a response even when adminstered a placebo.	80
2027682255	Blinding	Any individual associated with an experiment who is not aware of how subjects have been allocated to treatment groups.	81
2027682256	Placebo	A treatment known to have no affect.	82
2027682257	Confounding	Levels of one factor are associated with the levels of another factor in such a way that their effects cannot be separated.	83
2027682258	Sample Survey	A study that asks questions of a sample drawn from some population in the hope of learning something about the entire population.	84
2027682259	Bias	Any systematic failure of a sampling method.	85
2027682260	Randomization	The best defense against bias; each individual is given a fair, random chance of selection.	86
2027682261	Sample Size	Number of individuals in a sample represents the population.	87
2027682262	Census	Sample that consists of the entire population.	88
2027682263	Population Parameter	Numericlaly valued attribute of a model for a population.	89
2027682264	Representative	A sample is said to be ___________ if the stats computed from it accurately reflect the corresponding population parameters.	90
2027682265	Simple Random Sample (SRS)	A sample in which each set of "n" elements in the population has an equal chance of selection.	91
2027682266	SRS	Simple Random Sample	92
2027682267	Sampling Frame	List of individuals from whom the same is drawn.	93
2027682268	Sampling Variability	The natural tendency of randomly drawn samples to differ, one from another.	94
2027682269	Stratified Random Sample	A sampling design in which the population is divided into several subpopulations, or strata, and random samples are then drawn from each stratum.	95
2027682270	Cluster Sample	A sampling design in which entire groups are chosen at random.	96
2027682271	Multistage Sample	Sampling schemes that combine several sampling methods.	97
2027682272	Systematic Sample	A sample drawn by selecting individuals systematically from a sampling frame.	98
2027682273	Pilot	A small trial run of a survey to check whether questions are clear.	99
2027682274	Voluntary Response Bias	Bias introduced to a sample when individuals can choose on their own whether to participate in the sample.	100
2027682275	Convenience Sample	Consists of the individuals who are conveniently available to sample.	101
2027682276	Undercoverage	A sampling scheme that biases the sample in a way that gives a part of the population less representation.	102
2027682277	Nonresponse Bias	Bias introduced when a large fraction of those sampled fails to respond.	103
2027682278	Response Bias	Anything in a survey design that influences response.	104
2027682279	Random	If we know the possible values it can have, but not which particular value it takes.	105
2027682280	Simulation	Models a real-world situation by using random-digit outcomes to mimic the uncertainty of a response variance of interest.	106
2027682281	Simulation Component	A component uses equally likely random digits to model simple random occurrences whose outcomes may not be equally likely.	107
2027682282	Trial (Chapter 11)	The sequence of several componets representing events that we are pretending will take place.	108
2027682283	Re-expression	We _______ data by taking the logarithm, the square root, the reciprocal, or some other mathematical operation on all values of a variance.	109
2027682284	Ladder of Powers	Places in order the effects that many re-expressions have on the data.	110
2027682285	Correlation Coefficient	Numerical measure of the direciton and strength of a line or association.	111
2027682286	Scatterplot	Shows relationship between two quantitative variables measured on the same cases.	112
2027682287	Lurking Variable	A variable other than x and y that simultaneously affects both variables, accounting for the correlation between the two.	113
2027682288	Model	An equation of formula that simplifies and represents reality.	114
2027682289	Linear Model	An equation of a line. To interpret a linear model, we need to know the variables and their units.	115
2027682290	Predicted Value	The value of y^ found for a given x-value in the data. This is found by substituting the x-value in reg. equation.	116
2027682291	Residuals	Difference between data values and the corresponding values predicted by the regression model. Observed Value minus predicted value (e= y-y^)	117
2027682292	Least Squares	Specifics the unique line that minimizes the variance of the residuals or, equivalently, the sum of the squared residuals.	118
2027682293	Regression to the mean	Because correlation is always less than 1.0 in magnitude, each predicted y^ tends to be fewer standard deviation from its mean than its corresponding x was from its mean.	119
2027682294	Intercept	The intercept b (little o), gives a starting value in y-units. It's the y^ - value when x = 0.	120
2027682295	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.	121
2027682296	Leverage	Data points whose x-value are far from the man of x, are said to exert _____________ on a linear model.	122
2027682297	Influential Point	If omitting a point from the data results in a very different regression model.	123
2031495160	Disjoint(mutually exclusive)	2 events share no outcomes in common.	124