
Hi All
Is there anyone who can help with ANCOVA in SAS? Or this forum is inactive?
thanks 
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A simple breakthrough would be for SPSS (and other widely used software) to distinguish between those processes based on sampling theory (standard errors, significance etc.) and those that are simply analyses with numbers. The default should be the latter. Thus the menus would have comoparing means, correlations, regression and so on but not ttests,[Read more]

Dear all,
A student of mine has collected Thinkaloud protocols from student readers. He has codified the TAs using three categories and has tallied the number of strategies in each category. We are interested to find out if there is any relationship between the number of strategies used in each category and some of the students’ categorical variables[Read more] 
Hi,
I am looking for a recent reference that discusses the limitations of conducting survey research with nationally representative samples.
Monique 
Hi all
Is there anyone who can help with Yates correction example?
If the probablity of homozygote recessive (aa) from parents of (Aa) and (Aa) be 0.25, then the probablity of 2 out of 4 mating aa would be calculated using paired proportion
I wonder if we want to calculate the ZRatio by hand to compare to the software what would the numerator be[Read more] 
well, there’s a very simple reason for that: because that is not our purpose. methods and techniques developed by statisticians usually trickle down into other sciences to inform their practice, but then there’s this entity called “methodologist” which acts a “knowledge translator” of sorts trying to shape methods so that they become adequate to their[Read more]

Hi that is very true, as you said statistician publish the facts for themselves while clinicians want you to do things that are outdated
I wonder why statisticians go through too much pain to develop new methods then if they are not going to be used at some point in medical research?! 
it seems like that’s what (s)he’s after. it would have been nice for you to do a power calculation before and include that in your stats section. now if you did it and you did not include it i think it would be good for you to do so. but it seems like this person is attempting to use power analysis as a tool for data analysis through these[Read more]

Hi Oscar
Thanks for your attention. I quickly looked at the paper, so the reviewer wants me to do a “postexperiment” power calculation, which this paper calls “abuse of power”. Is that what you mean
does that mean I can just skip his question, so if I ever want to do this I would have to use the GPower right
thanks 
Hoenig, J.M. & Heisy, D. M.(2001) The Pervasive Fallacy of Power Calculations for Data Analysis. The American Statistician, 55(1), 1924.
so yeah, i added the extra bolded and underlined terms so you can kindly direct whoever told you that to a very wellwritten paper where both analytic and simulation results show that what this person is ask[Read more] 
Hello, I am back with another Power question!This time I have been asked a general power question and I am really confused about how to do this. here is the Q:
Given your small study size, and the fact that adherence to physical activity was low in both cases and controls, a type 2 error could occur. A power calculation should therefore be provided in the[Read more] 
the interaction seems like a more straightforward idea to me as well… i guess it also depends a little bit on what the person who’s asking you to perform this may have in mind… i mean for me, from a very pragmatic point of view, i would only care to see whether there is a differential effect of eating habits by gender in its ability to predict the[Read more]

Thanks alot Oscar I will order that from library and will see what I can do,,,I may end up doing a simple interaction analysis thought
🙂 
well… i really, really like my “Experiments: Planning, Analysis and Optimization” by Wu & Hamada published on the Wiley’s series collection in probability and statistics. i rarely use any other book outside from that one anymore…
if you’re familar with SAS you may wanna check out the ‘multicomp’ R package (i’m an R user) and you should be able to[Read more] 
Oh then if it is about writing the syntax I would rather use SAS, as I am aware its more powerful
by the way the ANOVA books you mentioned, do you have a specific one on mind?
thanks 
SPSS should be able to do that… testing for simultaneous linear contrasts is sort of standard practice…. you might need to work on this through syntax though because i’m guessing it’s a little bit hard to have a module specifically designed to create every possible set of contrasts for every possible design that’s out there… so you may need to do[Read more]

Oh well, I guess I have to go and read on creating a matrix, I am not sure if SPSS can do that
Thanks 
well… it’s just as when you learnt how to do contrasts in ANOVA/regression. you’d need to construct a matrix of contrsts (1’s, 1’s and 0’s) where in this case every coefficient is tested against the other one between groups (so the B coefficient of smoking for women is compared with the B coefficient of smoking for men and so on). the null hypothesis[Read more]

Thanks Oscar, much appreciated
and how do you “test a matrix of simultaneous contrasts”?
Sorry if I am so statnaive  Load More