STA2122
Introduction to Statistics I
Chapter 6:
Sampling Distributions
A
parameter
is a numerical descriptive measure of a population.
Because it is based on the
observations in the population, its value is almost always unknown.
A
sample statistic
is a numerical descriptive measure of a sample.
It is calculated from the
observations in the sample.
6.1 What is a Sampling Distribution?
Since, we usually wish to make inference about some population parameter, which is unknown,
we have to do so using a descriptive statistic obtained from a sample of the population in order to
make inference, but to do so we need the probability distribution of the sample statistic or the
sampling distribution.
The
sampling distribution
of a sample statistic calculated from a sample of
n
measurements is
the probability distribution of the statistic.
6.2 Properties of Sampling Distributions: Unbiasedness and Minimum Variance
A
point estimator
of a population parameter is a rule or formula that tells us how to use the
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 Fall '08
 STAFF
 Statistics, Normal Distribution, Standard Deviation, σx

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