Sneak Preview of Next Week
Next week we will be covering Chapters 4 and 6 (we will skip chapter 5 for now). Chapter 4 has some very important concepts in it. Please be sure to have read the chapter before class. On Thursday we will finish off Chapter 4 and then begin chapter 6 (and finish it up the following week (so there will be 2 homeworks for chapter 6). Homework for Chapter 4 will be 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.13, 4.14, 4.15, 4.20, plus an assignment using SPSS Syntax (more info later), and will be due on Friday the 15th by 5:00
Homework for first part of Chapter 6 will be 6.1, 6.3, 6.4, 6.8, 6.9, 6.10, 6.11, 6.13, 6.15, 6.17, 6.21, 6.22, 6.23 and will be due Tuesday the 19th during class.
Homework for the second part of Chapter 6 will be 6.24, 6.29, 6.32, 6.33 to 6.38 and will be due Friday the 22nd by 5:00
I will update the web pages a bit later - I just thought some of you might want this information ASAP.
Take care,
--Dr. M
posted by maclin_uni @ 10:19 AM
21 Comments:
Can you go over 4.6 in the homework?
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Dr. M,
Can you email the power point from today.... I need to see example of syntax.....thanks
Can you explain a little clearer what fixed marginals are - there is only a small paragraph about it in the book. Does that just mean that you have fixed numbers of subjects accross all groups you are comparing? I'm just a little confused about that. Also, if you have fixed marginals, how does that affect chi square calculations?
4.6... Take a look at what he is worried about in 4.2. He doesn't care whether he was charged correctly, only whether he was overcharged (maybe he's not very honest ;) ). If we were to make a graph of all the amounts they charged him (based on what he says in 4.2), where would he NOT want the average to fall? That's a hint for now; I'll provide more later if anyone still doesn't understand it.
Fixed marginals... I have to admit, I don't fully understand this either, certainly not to a point where I'd feel comfortable trying to teach it to someone else. I'll ask Dr. M. to explain.
Can you send out the Siegel syntax for the homework? I'm typing it incorreclty, but an error continues to appear. I must be missing a period or be off in the spaces. Much appreciated!
Fixed Marginals relates to the marginal totals (Totals for the levels of one variable summed across the levels of the other variable.) in the Chi-Square cells. When we analyze our samples we do not always know what these values are for the population so they are subject to chnages due to sampling error. When the marginal totals are known before the data are collected they are referred to as fixed marginal totals as they are not subject to sampling error. Other than that I wouldn't worry too much beyond a general understanding of the term(s). I doubt you will see them on the test unless we cover them more in depth in class.
I hope this helps,
--Dr. M
Syntax that worked on the version of SPSS on my laptop...
compute outcom1 = 1.
if ((group = 1) and rv.uniform(0,1) gt .5333) or ((group = 2 and rv.uniform(0,1) gt .5333)) outcom1 = 2.
execute.
Would it be possible to do some of the homework problems on SPSS in class (calculating chi square for one ways and contingency tables)? I have been trying to figure out how to get the same calculations on SPSS for the chi square as I get when I do it by hand and I'm at a loss. I've spent at least an hour trying to figure out how to get values that are reasonably close and have not been able to do it. Thanks.
I can do a couple of problems in class - which ones in particular would you like me to do?
--Dr. M
could you explain what it means when you look up the values in the chi square table. I can find the df and my chi square value but then i dont know how to interpret it once i look it up. does this number mean reject the null, accept it or what?
thanks
could you please explain some of the homework problems in class. I feel extremely lost when it comes to syntax and calculating chi square using SPSS. It is difficult to do the homework assignment for chapter 6 when I don't know where to begin after having the syntax lecture in class. Thank you!
to enter data into spss for the chi square calculation you can follow th directions on page 147 and 148 in howell
Reading the chi square table...
Let's pretend we have 6 df and we found a chi square value of 1.64.
Step 1) Locate the row with the correct number of degrees of freedom. In our example, go to the sixth row.
Step 2) Slide over to the right until you find the chi square value you calculated (or the nearest number listed). This would be the fourth column in our example.
Step 3) Look at the number at the top of the column (0.975 in our example). This is your p value. If p<.05, we reject the null hypothesis.
That should read "0.950 in our example."
In question 6.29 I am having a hard time figuring out what the expected value would be for the two groups....can somebody give me a hint?
it would be great if we could talk about 6.32 in class tomorrow.... I am getting a weird number for kappa..... thanks.
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I'll go over 6.32 in class - thanks,
Dr. M
Hi,
On 6.29 you do not have to calculate the expected values if you can figure out what the contingency table looks like. Based on the information provided, the table is a 2 x 2, with 2 levels of testosterone (high and normal)and 2 levels of behavior (Delinquent and non delinquent).
We are told that 10% if the 4016 men in the normal group had a record of delinquency (you will have to round numbers here) so the normal/ delinquency cell will have a frequency of 402 leaving 3614 for the normal/non delinquency cell.
Next we are told that 22.6% of the 446 men in the high testosterone group had a record of delinquency which gives us a frequency of 101 in the High/ delinquency cell and leaves us with 345 in the High/ non delinquency cell.
Set up your three columns in SPSS based on Howell's instructions for weighting cases (and what I covered in class) and you will get very similar values as are in the back of the book.
I hope that helps,
--Dr. M
I would like it if we could go over 6.24 d. and e. in class today. Thank you!
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