Stat 1000 Tips about Hypothesis Tests for the Mean
Published: Tue, 11/23/10
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Tips about Hypothesis Tests for the Mean
These tips apply to HW10 for those of you doing the distance/online version of the course. I assume the rest of you will also have similar questions on your next assignment.
Study Lesson 9 in my book, if you have it, to prepare for this topic.
First, be sure to note whether a question gives you σ, the population standard deviation, or s, the sample standard deviation. That dictates whether you will use z or t when making your confidence interval. I would assume, at this stage, you are likely to be given σ most of the time.
If you need to use JMP or Crunchit to test a hypothesis. Personally, I would use JMP. Click "New Data Table", then select "Edit" then "Paste with Column Names". Now select "Analyze", "Distribution" and highlight whichever column you are analyzing and click "Y, Columns", then click OK. You are now looking at a histogram and stuff. Click the red triangle next to the variable and select "Test Mean" from the drop-down list. Enter in the mean from your null hypothesis and enter in the given standard deviation. Click "OK" and JMP gives you the hypothesis test at the bottom of the printout. Look at my questions 13 and 14 for examples of how to read this printout.
If you want to use Crunchit! Copy the "http:..." stuff for the link to the data (shown at the top in your web browser) then select "Data" and "Load Data from URL". Paste the link into the box and make sure the box saying "use first line as column names" is selected. Make sure you also click the drop-down menu next to "Delimiter" and select "whitespace". Now, you should see the data given in two columns in your spreadsheet. Select "Statistics", then select "Z tests", then select "One-sample". In the pop-up window, make sure you click the appropriate variable in the "Variable" box to highlight it. Type the given standard deviation into the box and type in the mean you are using in your null hypothesis. Be sure you click whether you are doing a two-sided, upper-tailed (greater than) or lower-tailed test (less than) or else you will not be given the correct P-value. Click "OK". You now get a printout showing, among other things, the test statistic and P-value.
In either case (JMP or Crunchit!), you can now select, copy and paste your output to a file ready for upload as usual.
Make sure you read my section on P-values to learn how to properly interpret your P-value.
In question 6 in the Web Assign assignments remember the note I write after my question 4 talking about statistical significance versus practical significance. Also, remember the Law of Large Numbers taught in Lesson 7 of my book.