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#1




What statistical analysis to compare these two groups?
Self made.
======= A researcher has designed a retrospective study, where patients undergoing laparoscopic and open operations for right hemicolecomy are compared. He has identified 30,000 patients records from National Inpatient Sample Database and created similar groups of patients treated by laparoscopic (N=15,000) or open (N=15,000) approach with matching demographical characteristics. Within the laparoscopic group, 5% died and within open 15% died. if he wants to compare the immediate perioperative outcomes for mortality within these two groups, what statistical test should he use? a. Fisher's exact test b. Paired T test c. ChiSquare test d. ANOVA e. TwoSample T test f. Relative Risk
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#2




chi square because of the percentages?

#3




relative risk?
he wants to compare the same outcome [mortality] but in different procedures... open surgery is 3 x times more likely to die although relative risk is associated with cohort, which is a PROspective study, dunno :S whats the answer please , pm if u dont want to post it here now...
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#4




Dear DocSikorski
the correct answer is NONE! I know that you created this question... a. Fisher's exact test No for matched pairs b. Paired T test no for inference in proportions/rates c. ChiSquare test NO for matched pairs d. ANOVA no for inference in proportions/rates e. TwoSample T test no for inference in proportions/rates f. Relative Risk THIS is NOT a TEST. you should rewrite the question not using the "matched" assumption good luck to all! 
The above post was thanked by:  
drhma (05042012) 
#5




Quote:
great explanation good luck to u in whatever u are doing now these days
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The above post was thanked by:  
bebix (05042012) 
#6




Quote:
why not? to compare apples to apples you have to have groups matched....
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Ambition is a dream with a V8 engine. EP 
#7




I believe, that when you are able to write a good question  you really aced the topic.
Tests are my weak area, but I tried to make a good one
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Ambition is a dream with a V8 engine. EP 
#8




Quote:
Mc Nemar test or Logistic regression for matched p. test with robust standard errors, hahahaha... so, this is not only apple vs apple...this is apple vs apple´s sister!, hahaha 
#9




Quote:
haha ============= Multiple regression analysis will work for not matched groups, where all the comorbidites and risks, prior to surgery can be weighted individually to estimate the effect on the outcome... For matched groups: e.g. young patients with 01 comorbidites (low illness severity) of same races/ethnicity, gender and diagnosis (e.g. colon cancer will be most appropriate for right hemicolectomy, as I used in the question) Chisquare will work just fine (i used it several times), if there were less than 10pts that died in each, we could use Fisher's exact test, but thats kinda sample size that you don't wont to make a paper of haha
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Ambition is a dream with a V8 engine. EP Last edited by DocSikorski; 05042012 at 12:46 PM. 
#10




Note:
If you have only nominal variable do chisquare,if you have only interval variable go for correlation,one nominal and one interval go for ttest,but if you have more than 2 variables (at least one of each) go for anova 
#11




Quote:
So...anyone of your alternatives wasnt correct...dont worry, Im a Biostatistician and X2 does not work...maybe is time to go back to the books this is the bible for categorical analysis: http://www.amazon.com/StatisticalMe...6164393&sr=81 good luck! 
#12




Quote:
chi2 works only for independent samples in case of matched data, you must use McNamer test. good luck! 
#13




Thanks, I might ask my supervisor to order it...
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BiostatisticsEpidemiology, Step1Questions 
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