Standard Deviation
The
standard deviation
is a measure of variability in a sample
It tells us, “on average…how far are people from the mean”
It’s easier to do standard deviation by making a table first
Sampling Distribution
Sampling distribution has 2 important propterties that we want to remember
1. It has a mean that is equal to the population mean
2. It has a standard deviation that is equal to the population standard deviation
Confidence Interval
Now that we know how to calculate the SD, lets calculate a confidence interval for the avg. in the
distribution
We know…the mean of the sample means from repeated large samples, is the population avg. (CLT)
If I repeatedly sample 100 IU students and ask about GPA’s, the mean of the sample means (i.e. average
of GPA sample averages) is equal to the average population
Under ordinary circumstances, we are not able to repeatedly sample a population. This is where we use
confidence intervals.
To calculate the CI, we first estimate the
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This note was uploaded on 11/10/2011 for the course SOC 110 taught by Professor Latouche during the Fall '11 term at Indiana.
 Fall '11
 LaTouche

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