Inference for proportions
The Department of Statistics estimates that 50% of students at the University of Washington will have taken
STAT 311 by the time they graduate.
You believe it is less than 50%, and decide to take a survey of graduating
seniors to estimate the true proportion.
Your friend gets you a list of the graduating seniors and their email
addresses, and you randomly select a sample of n=200, email them, and ask them to report on a Catalyst
survey whether they have taken STAT 311:
40% of seniors report that they have.
Set up a 90% CI for the estimated proportion of seniors who have taken STAT 311.
With plug-in values:
State the null and the general alternative hypotheses. What is the approximate distribution of the sample
proportion under the null hypothesis?
(Specify the form of the null distribution, the mean and the standard
deviation, you do not need to solve for numerical value of the standard deviation).
Regardless of your answers above, set up a hypothesis test of
= 0.5 vs.
Test statistic in symbols
Test statistic with values
Is this a
We would reject the null when our test stat is