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Statistics
Definitions
34
Mathematics
12th Grade
06/26/2013

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Term
Individuals
Definition
the objects described by a set of data. Individuals may be people, animals, or things
Term
Variable
Definition
any charactereistic of an individual. A variable can take different values for different individuals
Term
Categorical Variable
Definition
Places an individual into one of several groups or categories
Term
Quantitative Variable
Definition
Takes numerical values for which it makes sense to find an average
Term
Distribution
Definition
the pattern of variation of a variable. It tells us what values the variable takes and how often it takes these values
Term
Inference
Definition
Drawing conclusions that go beyond thed ata at hand
Term
Frequency table
Definition
displays the counts (frequencies) of the variables in each format category.
Term
Relative Fequency Table
Definition
the data of that shows the percents of variables in each format category
Term
Roundoff error
Definition
The exact percents would add to 100, but the rounded percents only come close
Term
Pie Chart/ Bar Graph
Definition
Display the distribuiton of a categorical variable more vividly
Term
Two-way table
Definition
it describes two categorical variables
Term
Marginal Distribution
Definition
one of the categorical variables in a two-way table of counts is the distribuiton of values of that variable among all individuals described by the table
Term
Conditional Distribution
Definition
describes the values of that variable among individuals who have a specific value of another variable. There is a seprate conditional distribution for each value of the other variable
Term
Association
Definition
We say that there is an association between two variables if specific values of one variable tend to occur in common with specific values of the other.
Term
Simpson's Paradox
Definition
An association between two variables that holds for each individual value of a third variable can be changed or even reversed when the data for all values of the third variable are combined.
Term
Overal Pattern
Definition
you can describe the overall pattern of a distribution by its shape, center and spread
Term
Depatures
Definition
An important kind of depature is an outlier, an individual value that falls outside the overall pattern
Term
Skewness/Symmetric
Definition
either mirrored or much longer on one side
Term
Unimodal
Definition
They have a single peak: minor ups and downs in a graph, like the "bumps"
Term
Bimodal
Definition
It has two clear peaks
Term
Multimodal
Definition
More than two clear peaks
Term
Stemplots
Definition
give us a quick picture of the shape of a distribution while including the actual numerical values in the graph.
Term
Histogram
Definition
The most common graph of distribution of one quantitative variable.
Term
Mean
Definition
adding the values together and dividing by the number of observations
Term
Median
Definition
is the midpoint of a distribution, the number such that half the observations are smaller and the other half are larger.
Term
The 1.5 X IQR rule for outliers
Definition
Call an observation an outlier if it falls more than 1.5 x IQR above the third quartile or below the first quartile
Term

Five-number Summary

 

Definition

A distribution consists of the smallest observation, the first quartile, the median, the third quartile, and the largest observation, written in order from smallest to largest. In symbols, the five-number summary is

Minimum Q1, M Q3 Maximum

Term
Standard Deviation
Definition
measures the average distance of the observations from their mean. It is calculated by finding an average of the squared distances and then taking the square root.
Term
Variance
Definition
The average squared distance
Term
pth Percentile
Definition
a distribution of the value with p percent of the observations less than it
Term
Standardized value (z-score)
Definition

If x is an observation from a distribution that has known mean and standard deviation, the standardized value of x is

Z=x-mean/standard deviation

A standardized value is often called a z-score

Term
Density Curve
Definition
is a curve that is always on or above the horizontal axis, and has area exactly 1 underneath it. It describes the overall pattern of a distribution.
Term
Normal distribution and normal curve
Definition
is described by a Normal density curve. Any paticular Normal distribution is completely specified by two numbers; its mean and standard deviation. The mean of a Normal distribution is at the center of the symmetric Normal curve.
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