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Statistics
how collect, organize, analyze, and interpret data
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Goal
drawing conclusions from small group of elements (the sample) about a larger group of elements
(thepopulation)
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Mean (Average)
Sum of All the Entries Divided by the Number of Entries
largely influenced by extreme values
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Median
Central Value of an Ordered Data - not affected by few extremely large (small) values
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To find the median
rank order data in ascending order
n is odd: median is the central value
n is even: median is the average of two central values
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Mode
Value With Highest Frequency (most often value in the data set)
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Sample Range
Largest value Smallest value
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Sample Variance s2
average squared deviation from the mean
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Sample Standard Deviation s
most often used - characterizes average difference of individual values in the data set from its mean.
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Sample Correlation Coefficient r
measure of strength of a linear association between two variables.
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Probability
number between 0 and 1 to indicate the likelihood of an event
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An experiment
any process that produces an observation or outcome
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A sample space
all outcomes possible of an experiment
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An event
any set of outcomes
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Probability of an event A: P(A)
chance that the outcome of the experiment is contained in A.
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independent events
the probability of event B does not depend on occurrence of event A
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Dependent events
the probability of drawing the ace as the second card depends on drawing the first card P(B given A)
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event A and B
all outcomes that are in A and B at the same time
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event A or B
when both events occur, or either one of them: A or B= {(h,h),(h,t), (t,t)}
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complement of an event (not A)
all outcomes that are not in A
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A random variable
takes on numerical values that are associated with a probability, defined by a probability distribution
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Discrete random variables
(possible to list all values), number of defect radios in a lot, daily car buys in a dealership,
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Continuous
all values in some interval are possible
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Confidence Interval Estimation
we know data from a sample, our task is to evaluate population parameter
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Hypothesis testing
we know what the population parameter should be null hypothesis and we have sample data