Stat 2000: Tips for Web Assign HW 02
Published: Mon, 01/24/11
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Tips for Web Assign HW 02
When working with Web Assign, always enter the answer to one specific box and then click "Submit Answer" to confirm that is correct before you move on to another box. Do not enter several answers all at once in several boxes before you click "Submit Answer". You risk being marked wrong due to some typo or something.
For some strange reason, JMP 8 occasionally computes wrong answers even if you have copied and pasted your data correctly. I suggest that, if it is feasible, type the given data into your calculator (in Stat mode as shown in Appendix D of my book), and have your calculator compute the sample mean. Compare that answer with JMP's answer for the sample mean. If they are the same, everything is fine. If they are not the same, close JMP 8 and restart it, recopy and paste the data, and check again. Sometimes you have to do this 2 or 3 times before JMP finally works. If it is not feasible to use your calculator to compute the sample mean, have JMP do the question 2 or 3 times, being sure to restart JMP and recopy the data each time, and confirm that JMP gives you the same answer each time before risking entering the results into Web Assign.
If you are taking the course by distance/online (Section D01) click here to see your tips for HW 02.
Again, this assignment focuses on Lessons 1 and 2 in my study book. The difference is that now you are using t instead of z because σ, the population standard deviation, is not given. Be especially sure to study the last two questions in Lesson 2 of my book where I teach how to test hypotheses for matched pairs.
Question 1 is standard stuff for a student who has studied my lessons.
Question 2 (phone range):
Personally, I would not bother stacking this data like they suggest (good luck even successfully copying it and pasting it at all). I would merely type the data in manually.
Open a "New Data Table" in JMP. Double-click "Column 1" and name it something like "distance". Make sure the "data type" is numeric and the "modeling type" is continuous, and click OK. Now type the given data into the column on the spreadsheet and make sure you don't make a mistake.
If you insist on copying and stacking the data, here's how: Copy and paste the given data into a New Data Table in JMP. In the toolbar at the top, select "Tables", then select "Stack". Highlight all of the columns in the "Select Columns" box and click "Stack Columns" and click OK. You will now see all of the data stacked into one column (there will be another column showing all the column names which you can ignore). Name the column something like "distance" and make sure its Data Type is Numeric and its Modeling Type is Continuous. Click OK.
To get JMP to make confidence intervals for the mean:
Select "Analyze, Distribution" from the toolbar at top. Highlight the column you are interested in ("distance" in this case) and click the "Y, Columns" button. Click OK. You are now taken to a window showing a histogram and stuff. To get a confidence interval, click the red triangle next to your column variable directly above the histogram to get a drop-down list and select "Confidence Interval". In the pop-up window that appears, select "Other" (even if the level of confidence you desire is in the list) and type in the level of confidence you want (in decimal form, so 95% is 0.95). Make sure "Two-sided" is selected. You are not given a value for sigma in this question, so make sure the "Use known Sigma" checkbox is not selected. Click OK. A Confidence Intervals table will appear in your output screen at the bottom.
To get JMP to test hypotheses for the mean:
To test a hypothesis, click that same red triangle you used to make a confidence interval and select "Test Mean". Type in the value the null hypothesis believes the mean to be and type in the known value of sigma, if you have one (otherwise leave that value blank). Click OK. A Test Mean = Value table appears in your output where, among other things, JMP gives you the test statistic and three probability values. Those three probabilities are the P-value for the three possible alternative hypotheses. JMP will use a z statistic if you are given a sigma value to enter or a t statistic if sigma is unknown.
Prob > |t| is the two-tailed P-value.
Prob > t is the upper-tailed P-value.
Prob < t is the lower-tailed P-value.
To get rid of any outputs you don't want to copy and paste, click the red triangle and deselect the unwanted things.
To copy and paste the parts of a JMP printout you do want, select the icon on the JMP toolbar that looks like a fat white plus sign "+" (the Selection tool). You can then click various parts of the printout to select the sections you want. Copy and paste into Word or something like that.
Question 3:
Make sure you are examining this data correctly! Again, look at my last two questions in Lesson 2. Use your calculator in Stat mode to work out the mean and standard deviation (see Appendix D in my book how to do this on your calculator).
Study Lesson 3 in my book before you start this assignment.
Questions 3 to 6 should go quite smoothly for a person who has studied Lesson 3 in my book.
To be able to understand questions 7 and 8, you will need to read my "Errors in Hypothesis Testing Revisited" section in Lesson 6 of my study book (this is only in the 2010-2011 edition, blue cover). You may also need to skim through some of the earlier questions in Lesson 6 to get a grasp of how to compute Discrete Probabilities and Binomial Probabilities. I think mastery of these topics is not important at this time, you will get an opportunity to learn this lesson more thoroughly later on in this course.