# Shared Flashcard Set

## Details

Statistics Vocab
for test
129
01/14/2013

Term
 Estimate
Definition
 The process of making an educated guess about a probable value or the result of that guess.
Term
 Inferential Statistics
Definition
 A subset of statistics composed of methods that use descriptive statistics to make educated guesses (infer) about population values.
Term
 Emperical Data
Definition
 Data that has been observed or created via experimentation; real data, not theoretical.
Term
 Statistics
Definition
 The scientific discipline that investigates a wide variety of methods for extracting information from data.
Term
 Measurement
Definition
 The result of ascertaining the size or extent or boundaries of some item of interest using a scaled instrument in units that are commonly understood.
Term
 Statistic
Definition
 A value or definition that describes a characteristic of a sample.
Term
 Descriptive Statistics
Definition
 A subset of statistics composed of methods that seek to summarize, describe and visualize raw data in order to extract data from it.
Term
 Mutually Exclusive
Definition
 With reference to sorting observations into classes or categories, the property that each observation can fit into one and only one defined category or class. See collectively exhaustive.
Term
 Data Set
Definition
 A collection of facts often about different individuals and often about different characteristics of those individuals.
Term
 Stratified Sampling
Definition
 A method of sampling used on a population that is divided into mutually exclusive, collectively exhaustive subgroups by some characteristic of interest (strata). The full sample is composed of simple random samples from each subgroup.
Term
 Response Error
Definition
 Measurement error due to respondents giving false information.
Term
 Sample
Definition
 A subset of all the defined items of interest in existence in the universe of the question asked.
Term
 Categorical Data
Definition
 Observations which record the presence or absence of a particular characteristic in the individual from which information is sought; for example, an individual's marital status, gender or national origin.
Term
 Continuous Data
Definition
 A list of observations that were measured and which could take on any possible value in an interval, even if the technology is not available to measure the infinitely small differences.
Term
 Convenience Sampling
Definition
 A method of selecting individuals for a sample which is as simple and inexpensive as possible, a sample which is easily found.
Term
 Non Probability Sample
Definition
 A sampling method where the likelihood of any member of the population being selected for a sample is unknown.
Term
 Variable
Definition
 Something that changes; in statistics it usually refers to a particular characteristic of the individual or item studied that varies from individual to individual.
Term
 Non Random Sampling
Definition
 Non probability sampling.
Term
 Collectively Exhaustive
Definition
 With reference to sorting observations into classes or categories, the property that each observation has a defined category or class into which it fits. See mutually exclusive.
Term
 Judgement Sampling
Definition
 Selecting a group of individuals for study based on the opinion of an "expert;" a non-probability sample.
Term
 Random Sampling
Definition
 Probability Sampling
Term
 Ordinal Data
Definition
 Observations from ranking systems. The underlying concept of interest is qualitative, however, the inclusion of a ranking implies differences in the "amount" of the quality in the individual. For example, if ranking the satisfaction of one's contact with an account manager at AT&T one might select from choices such as "Very Poor," "Poor," "Acceptable," "Good" or "Very Good."
Term
 Discrete Data
Definition
 Data that is the result of a count and is represented by non-negative integers.
Term
 Random Numbers
Definition
 Numbers the value of which is determined by chance alone.
Term
 Population
Definition
 All defined items of interest in existence in the universe of the question asked.
Term
 Simple Random Sample
Definition
 A type of probability sampling where the likelihood of any member of the population being selected for a sample is known and equal.
Term
 Observation
Definition
 A datum
Term
 Individual
Definition
 A specific, individual entity of interest; a person, a firm, a DVD.
Term
 Census
Definition
 A recording of information about specific characteristics of an entire population.
Term
 Cluster Sample
Definition
 A method of pseudo random sampling in which locations are randomly selected and, because the individuals of interest tend to gather or cluster at specific, known locations, all of the individuals at the selected locations are measured or sampled.
Term
 Numerical Data
Definition
 Observations from counts or measurements that are reported as numbers and on which mathematical operations can be performed.
Term
 Probability Sample
Definition
 A sampling method where the likelihood of any member of the population being selected for a sample is known.
Term
 Measurement Error
Definition
 Error introduced into a sample by the use of leading or ambiguous questions, the tone used by an interviewer which influences a respondent to make a particular choice, or respondent reporting false information.
Term
 Parameter
Definition
 A value or definition that describes a population; a fact about a population.
Term
 Nominal Data
Definition
 Information gathered by defining qualitative characteristics as having one of a number of specific subset qualities, each identified by a descriptive label or name. For example, a question about "Marital Status" would anticipate the respondent to select from the most accurate category of "Never Married," "Married," "Divorced" or "Other."
Term
 Data
Definition
 A "datum" is a single fact; data is a collection of similar facts about different individuals.
Term
 Systematic Sampling
Definition
 A sampling method used on a population which can be listed completely and/or may have some inherent linear order. The first item is selected at random then subsequent items are selected at pre-determined fixed intervals starting with the first item.
Term
 Ordered Array
Definition
 A data set which has been sorted in some orderly manner, most often by value from smallest to largest value.
Term
 Frequency Polygon
Definition
 A "line" chart of a quantitative variable which is created by plotting class marks and the frequencies associated with each class. Frequencies are on the Y-axis and class marks are along the X-axis. By definition, such a chart is "closed" indicating that the line connecting the points begins at (0,0) and ends at (X,0), where X is the class mark of the class which would follow the largest class to have a non-zero frequency.
Term
 Absolute Frequency
Definition
 A simple count of the items of interest.
Term
 Outlier
Definition
 An extreme or unusual observation. By definition in this course a value that is more than 3 standard deviations away from the mean of the data set.
Term
 Relative Frequency
Definition
 The frequency of an event or value expressed as a percent of the whole or as a proportion; the absolute frequency divided by the total number of observations in the data set.
Term
 Symmetric
Definition
 Refers to a visual representation which, when divided at the midpoint, creates one side which is the mirror image of the other.
Term
 Stem-and-Leaf Plot
Definition
 A graphical display of a quantitative data set that orders the data sequentially then presents the data in a series of rows. Each row has a common "stem" value which is stated at the beginning of the row. A vertical line separates the common stem from the list of final digits from each observation with that stem (leaves), also ordered sequentially.
Term
 Dispersion
Definition
 The idea of how much observations in a given data set are alike or different from one another, or how much they vary. Often referred to as "spread" (the idea of how much 'territory" the data set covers), but can also be refered to as homogeneity, stability, and other ideas which represent similarity, difference or variation.
Term
 Frequency Distribution
Definition
 A table which summarizes a quantitative variable, composed of rows of classes accompanied by frequencies which represent the occurrence of values of the variable found in a particular class.
Term
 Shape
Definition
 A term that refers to how symmetric a distribution is and which may include other information about distinctive visual characteristics of the distribution, for example, that the distribution is bimodal.
Term
 Stem
Definition
 All digits of an observation placed into a stem-and-leaf plot except the last. If an observation was 589, the stem would be 58.
Term
 Central Tendency
Definition
 The inclination of a data set to either cluster around a value on the number line, to have an easily located "half-way point" or to find a visual balance point.
Term
 Histogram
Definition
 A "column" chart of a quantitative variable which has classes along the X-axis and frequencies along the Y-axis. The data are represented by columns that have the same width, which is the class interval, and the height corresponding to the frequency.
Term
 Left-Skewed
Definition
 A data set that is not symmetric, specifically, one that has at least one unusually small observation which draws the mean down to a value lower than the median. Also referred to as "negative skewed." Such data would have a negative coefficient of skewness.
Term
 Leaf
Definition
 The last digit of an observation placed into a stem-and-leaf plot. If an observation was 589, the leaf would be 9.
Term
 Ogive
Definition
 A "line" chart of a quantitative variable which is created by plotting upper class limits and the cumulative frequencies associated with each class. Frequencies are on the Y-axis and class limits are along the X-axis. By definition, such a chart begins at (0,0).
Term
 Cumulative Relative Frequency
Definition
 As one moves through a table from top to bottom, a cumulative relative frequency is the relative frequency of the current class plus the sum of the relative frequencies of all previous classes.
Term
 Frequency
Definition
 A count or similar value which represents how often a specific event or value occurs.
Term
 Pie Chart
Definition
 A chart of categorical data in which each category is represented by a wedge of a circle representing the entire data set. The size of the wedge conforms to the relative frequency of the items in a particular category.
Term
 Pareto Diagram
Definition
 A specialized "column" chart of categorical data which has categories arranged on the X-axis from highest frequency on the left to lowest frequency on the right.
Term
 Cumulative Frequency
Definition
 As one moves through a table from top to bottom, a cumulative frequency is the absolute frequency of the current class plus the sum of the absolute frequencies of all previous classes.
Term
 Class
Definition
 A numerical category created by specifying an interval along a number line, such as the interval from 0 to 1, or from 5 to 10.
Term
 Class Limits
Definition
 The end points of a class which specify exactly which values fit into the class.
Term
 Scatter Plot
Definition
 A graphical representation of paired data, with one variable on the X-axis and the other on the Y-axis. The specific xi and yi values for a particular individual form the cartesian coordinates for one point on the graph.
Term
 Distribution
Definition
 A complete description of a variable, achieved by plotting a graph of its values, by stating a mathematical function which describes the variable, or by stating a measure of center, dispersion and shape of the variable.
Term
 Class Mark
Definition
 The midpoint of the class, the mean of the class limits.
Term
 Bar or Column Chart
Definition
 A graphical representation of categorical data, in which each column or bar represents a specific category and its height (column) or length (bar) represents the frequency of data which fall into that category. (Columns are "vertical bars.") Such frequencies can be absolute or relative. The columns or bars are the same width, but are not so wide as to touch the column or bar of the category which follows, thus, there is space along the axis between each bar or column.
Term
 Class Interval
Definition
 The distance from the class' lower limt to its upper limit.
Term
 Right-Skewed
Definition
 A data set that is not symmetric, specifically, one that has at least one unusually large observation which draws the mean up to a value higher than the median. Also referred to as "positive skewed." Such data would have a positive coefficient of skewness.
Term
 Bimodal Distribution
Definition
 A distribution with more than one modal value. In general, it refers to a graphical representation of a data set which has two "local" peaks, which do not have to be of the same height but must be higher than the surrounding area.
Term
 Median Class
Definition
 The class in a frequency distribution which contains the median value, often determined as that class for which the cumulative relative frequency crosses 0.5.
Term
 Deviation
Definition
 Specifically, the difference between the value of an observation and the mean of the observation's data set, (xi - Âµ). "Deviation" generally refers to the difference between an observation and some central value.
Term
 Grouped Data
Definition
 Data which has been put into a frequency distribtuion but for which the actual observed values are not available.
Term
 Population Mean
Definition
 The arithmetic average value of a population.
Term
 Median
Definition
 The physical midpoint of an ordered array.
Term
 Resistant
Definition
 A statistic is said to be resistant if it is not influenced by extreme values. See sensitive.
Term
 Sensitive
Definition
 A statistic is said to be sensitive if it is influenced by extreme values. See resistant.
Term
 Mode
Definition
 The most frequently occuring value in a data set, of which there may be more than one.
Term
 Multimodal Distribution
Definition
 A distribution with more than one modal value. In general it refers to a graphical representation of a data set which has more than one "local" peak; the peaks do not have to be of the same height but must be higher than the surrounding area.
Term
 Weighted Mean
Definition
 A method of calculating the mean of a data set, where each particular value in the set is "weighted" by how often it appears in the data set. This method is particularly useful for data sets that have many repeated values. The result is identical to the arithmetic average of the data set.
Term
 Sample Mean
Definition
 The arithmetic average of a sample.
Term
 Modal Class
Definition
 The class in a frequency distribution which has the highest frequency.
Term
 Variance
Definition
 The average squared distance between all observations in a data set and their mean; a measure of dispersion.
Term
 Percentile
Definition
 The value in a data set below which fall a specified percentage of the observations in a data set.
Term
 Mean Absolute Deviation
Definition
 The sum of the absolute value of the deviations in a data set, divided by the number of deviations, a measure of dispersion.
Term
 Interquartile Range
Definition
 The difference between the first and third quartiles of a data set, specifically, Q3 - Q1; a resistant measure of dispersion.
Term
 Quartile
Definition
 The values below which fall 25, 50 and 75 percent of the observations in a data set. See percentiles.
Term
 Range
Definition
 The difference between the maximum and minimum values of a data set, a measure of dispersion.
Term
 Standard Deviation
Definition
 The average distance between all observations in a data set and their mean; the square root of the variance; a measure of dispersion.
Term
 Coefficient of Variation
Definition
 A unit-free measure of dispersion which expresses the standard deviation of a data set as a percentage of the mean of the data set.
Term
 Homogeneity
Definition
 The same, possessing the same qualities.
Term
 Skewness
Definition
 Degree of symmetry.
Term
 Negative Skewed
Definition
 A data set that is not symmetric, specifically, one that has at least one unusually small observation which draws the mean down to a value lower than the median. Also referred to as "left-skewed." Such data would have a negative coefficient of skewness.
Term
 Positive Skewed
Definition
 A data set that is not symmetric, specifically, one that has at least one unusually large observation which draws the mean up to a value higher than the median. Also referred to as "right-skewed." Such data would have a positive coefficient of skewness.
Term
 Chebyshev's Theorem
Definition
 The theorem provides a method for predicting the minimum percent of values that will fall within plus and minus a selected number of standard deviations from the mean. The number of standard deviations must be greater than 1. The theorem applies to any data set for which a mean and a standard deviation can be calculated. Sometimes spelled "Tchebycheff" or "Chebychev."
Term
 Empirical Rule
Definition
 A method for approximating broad probabilities for bell-shaped, symmetric distributions. Same as Normal Rule.
Term
 Normal Rule
Definition
 A method for approximating broad probabilities for bell-shaped, symmetric distributions. Same as Empirical Rule.
Term
 Heterogeneity
Definition
 Different, possessing different qualities.
Term
 Slope
Definition
 The rate of change of a line, specifically the change in Y for a unit change in X.
Term
 Least Squares Line
Definition
 The line which results from minimizing the sum of squared error when error is defined as the distance between an observed yi value and the predicted y'i value at the same xi.
Term
 Correlation Coefficient
Definition
 A unit-free measure of the strength of a possible linear relationship between a pair of variables.
Term
 Causal
Definition
 A relationship between two variables where one variable (the causal, independent, regressor, predictor or explanatory variable) directly produces an effect on the other variable (the response, dependent, predicted or explained variable.)
Term
 Covariance
Definition
 A measure of the strength of a possible linear relationship between a pair of variables.
Term
 Residual
Definition
 Left over; estimated error.
Term
 Spurious
Definition
 False, counterfeit or artificial.
Term
 Intercept
Definition
 The value on the Y-axis where a given line crosses the axis.
Term
 Dependent Variable
Definition
 The variable in a causal relationship that is being effected by the other variable or other variables.
Term
 Linear
Definition
 Describing or pertaining to a line; a function of variables that does not exceed the first degree.
Term
 Independent Variable
Definition
 The variable or variables in a causal relationship that effect the dependent variable.
Term
 Event
Definition
 A subset of outcomes of interest, for example, if rolling a die, getting an even number is a possible event, which consists of the subset 2, 4, 6.
Term
 Probability of an Event
Definition
 A mathematical statement of the relative certainty or uncertainty that an event will occur.
Term
Definition
 The probability of at least one event of multiple events occurring can be calculated by summing the probabilities of the individual events and subtracting the probability of any intersection or overlapping of the events.
Term
Definition
 When outcomes are mutually exclusive, the joint probability of those outcomes is the sum of their individual probabilities.
Term
 Classical Probability Approach
Definition
 The approach to probability that derives probabilties of events using theory or mathematics.
Term
 General Law of Multiplication
Definition
 The joint probability of two events can be calculated by multiplying the probability of one given the other has occurred with the probability of the other event, P(A & B) = PA|B)*P(B). For example, if a restaurant notes that 70% of its customers use mustard (P(B))and that 55% of those who use mustard also use ketchup (P(A|B)), the probability that a customer uses both mustard and ketchup (P(A&B)) is 55%*70% = 38.5%.
Term
 Conditional Probability
Definition
 The likelihood of an event given that another event has happened or is true.
Term
 Simple Probability
Definition
 The likelihood of a single event occurring, a marginal probability.
Term
 Independence Rule
Definition
 Describes two events when the fact of the occurrence of one has no effect on the probability that the other will occur.
Term
 Joint Probability
Definition
 The probability that two or more events happen simultaneously or occur in the same subject.
Term
 Special Law of Multiplication (Independent Events)
Definition
 When two events are independent, the general law reduces to this special law of multiplication: joint probabilities of two independent events are the product of their simple probabilities.
Term
 Contingency Table
Definition
 A cross-tabulation of two variables measured from the same set of individuals, rather like a merging of two frequency distributions. Categories or classes are designated horizontally for one variable and vertically for the other, creating "cells" which represent one horizontal category and one vertical category jointly. The observations are sorted and placed in appropriate cells based on their particular combination of categories.
Term
 Combination
Definition
 A unique group of observations drawn from a large set. The order of the observation values is irrelevant, thus the same observations drawn in a different order would not be a new combination.
Term
 Sample Space
Definition
 The list of all possible results of an experiment which depends on chance to determine outcomes.
Term
 Complement
Definition
 To complete, or that which completes. In terms of probability the complement is the subset of all outcomes which are NOT part of an event which has been defined as being of interest. For example, if when rolling a die, the event of interest is getting an even number and consists of outcomes 2, 4 and 6, the complement is the subset of the odd numbers, 1, 3 and 5.
Term
 Independent Events
Definition
 Outcomes which have no effect on another outcome occurring.
Term
 Dependent Events
Definition
 Describes two events when the fact of the occurrence of one affects the probability that the other will occur.
Term
 Marginal Probability
Definition
 The likelihood of a single event occurring, a simple probability.
Term
 Intersection
Definition
 The subset of outcomes which belong to more than one event.
Term
 Objective Probability
Definition
 Classical or empirical probabilities, those which do not depend on the opinion of a person or persons.
Term
 Experiment
Definition
 A test or trial in which at least some of the conditions are under the control of the observer, conducted to gather evidence of behavior or specific results.
Term
 Subjective Probability
Definition
 Probabilities that are derived at least partly based on the opinion of an expert or experts.
Term
 Empirical Probability Approach
Definition
 The approach to probability that derives probabilties of events from experiment or observations of real events.
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