This preview shows pages 1–2. Sign up to view the full content.
Stats: Estimating the Mean
You are estimating the population mean, mu, not the sample mean, x bar.
Population Standard Deviation Known
If the population standard deviation, sigma is known, then the mean has a normal (Z)
distribution.
The maximum error of the estimate is given by the formula for E shown. The Z here is the z
score obtained from the normal table, or the bottom of the ttable as explained in the introduction
to
estimation
. The zscore is a factor of the level of confidence, so you may get in the habit of
writing it next to the level of confidence.
Once you have computed E, I suggest you save it to the memory on your
calculator. On the TI82, a good choice would be the letter E. The reason for
this is that the limits for the confidence interval are now found by
subtracting and adding the maximum error of the estimate from/to the
sample mean.
Student's t Distribution
When the population standard deviation is unknown, the mean has a Student's t distribution. The
Student's t distribution was created by William T. Gosset, an Irish brewery worker. The brewery
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
This is the end of the preview. Sign up
to
access the rest of the document.
 Spring '08
 AKBAS
 Statistics, Standard Deviation

Click to edit the document details