Statistics Help @ Talk Stats Forum - Biostatistics
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Epidemiology and biostatistics, public health research. GLM, logistic regression, survival analysis, clinical trials.enMon, 31 Aug 2015 21:06:40 GMTvBulletin60http://www.talkstats.com/images/misc/rss.pngStatistics Help @ Talk Stats Forum - Biostatistics
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analysis for sparse contingency table
http://www.talkstats.com/showthread.php/62260-analysis-for-sparse-contingency-table?goto=newpost
Mon, 31 Aug 2015 18:58:44 GMTI am analyzing a 2x2x3x2 contingency table. The covariates are treatment (2 different kinds, TR1 and TR2, both binary), location of treatment (3...I am analyzing a 2x2x3x2 contingency table. The covariates are treatment (2 different kinds, TR1 and TR2, both binary), location of treatment (3 levels A, B, C), and the outcome is an event that either occurred or did not occur. The table is large compared to the sample size, and observing the event is rare, so the table is quite sparse. However, there does appear to be a strong interaction between the outcome and the covariates of interest.

Some of the suggested strategies were adding a small constant to all zero cells, and/or adjusting the degrees of freedom to account for the zeroes. I was planning on doing some kind of log-linear analysis. I am not too experienced with this kind of analysis so any help would be welcome. Thank you.
]]>Biostatisticsjpluta26http://www.talkstats.com/showthread.php/62260-analysis-for-sparse-contingency-tableSample size calculation for Chi square Test
http://www.talkstats.com/showthread.php/62243-Sample-size-calculation-for-Chi-square-Test?goto=newpost
Sun, 30 Aug 2015 13:03:56 GMTHi, I have trouble determining the sample size for a simple Chi Square Test.
My problem is the following:
I tried to calculate the sample size for...Hi, I have trouble determining the sample size for a simple Chi Square Test.
My problem is the following:
I tried to calculate the sample size for two samples whith P1=0.7 and P2=0.9. Unfortunately, the result was different when I used another software. I simulated the data and did the Chi Square test in SPSS and the results were not even close to 0.05 even though I set alpha to 0.05.
My questions are now:
- which software is the best fo sample size calculations?
- what is the appropriate number of cases for this problem for each group?
- how do you calculate the sample size for proportions of more than 2 groups (e.g. 2x3 table)

Thanks so much for your help!
]]>Biostatisticsehi895http://www.talkstats.com/showthread.php/62243-Sample-size-calculation-for-Chi-square-Test