Feb 812, 2010
Review:
We have two objectives in this tutorial. You will use Normal/t distribution commands learned
from last week’s tutorial.
Confidence Interval Estimate:
A sample mean

x
is always used as a
point
estimate of a population mean
μ
. However, as the
population is not exactly same as the sample, error always exists when we use

x
to forecast
μ
.
Therefore, we introduce a confidence interval estimate of the population mean. In other words, I
would rather say “
μ
is between 0.5 and 0.7” than “
μ
is equal to 0.6”.
How to calculate the confidence interval estimator of a population mean
μ
? There are two
cases:
Case 1: If the population standard deviation
σ
is known, use a normal distribution:
Case 2: If the population standard deviation is unknown, use the sample standard deviation
and a
t
distribution:
Hypothesis Testing for a Population Mean if the Population Standard Deviation is Known:
Step 1: What’s your H
0
and H
1
?
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 Spring '11
 tanaka
 Statistics, Normal Distribution, Standard Deviation, Statistical hypothesis testing

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