Problem Set 12 Hints

Firstly, know that EVERY problem MUST have a population parameter (p or mu), sample parameter (x-bar or p-hat), standard deviation (given for means but must be calculated for proportions), and a number of observations which is always n. In some problems it may not be obvious, for example, the problem might use language like "a majority of..." in which case you must think for yourself what a "Majority" looks like as a percentage or as a decimal. Think about it....

Problem One:
The little thing that looks like the Jesus fish is the Greek letter lowercase alpha, which is often used in stat to represent the level of significance. So for example, if alpha = .05 then the problem is using a 5% level of significance.

Problem Two:
Think carefully about which number is which. Remember that your population parameter always comes from the bigger group. NO SHORTCUTS - tell me specifically in CONTEXT what all the assumptions are, and remember that your interpretation is going to require two sentences with the significance test.

Problem Three:
a. I'm looking for a fantastic CUSS here. Label your graph properly. A rough sketch of the histogram is fine but give me an idea of scale. As Toni suggested, starting with "54" probably isn't a good idea - start with something more even.
b. Since the n is so small here, I don't want to hear anything about how we can use the "central limit theorem" in this problem because....we can't. Show WHY we can't and tell me what else we can do (then do that).

Problem Four:
a. use "fewer than half" as a reference for what values you should use for p, your population parameter
b. please do the whole significance testing procedure again for this part
c. DON'T SKIP THIS QUESTION - I know that for about half of you you're going to think about skipping it. It's worth 10 points and will knock you down a letter grade if you skip. Instead, think carefully about what is happening between a and b and tell me what you observe. Write a congratulations to Erin and/or Drew for making state choir after this question for five bonus points. If you get stuck with this question, just ask someone for help.

Problem Five
Do two different significant tests for this question, and think carefully about what "a majority" means. If you got the last question, you'll know what I'm talking about. If not, ask a friend or me for help.