Wojtek
  • Member for 11 years, 5 months
  • Last seen more than 6 years ago
  • Lodz, Poland
Under what conditions does correlation imply causation?
9 votes

Almost always in randomized trials Almost always in observational study when someone measure all confouders (almost never) Sometimes when someone measure some counfounders (IC* algorithim of DAG ...

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What dependence is implied by a chi square test for independence?
4 votes

There are two definitions of statistical independence: 1) P(A,B)=P(A)*P(B) <=> 2) P(A|B)=P(A) <=> 2a) P(B|A)=P(B). (<=> means if and only if) So to answer your question: both are valid. ...

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Relationships between two variables
4 votes

Another solution to your problem (without transforming variables) is regression with error distribution other then Gaussian for example Gamma or skewed t-Student. Gamma is in GLM family, so there is a ...

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Determine if three is statistically different than ten for a very large number of observations (1,000,000)
4 votes

In this case Poisson is good approximation for distribution for number of cases. There is simple formula to approximate variance of log RR (delta method) . log RR = 10/3 = 1.2, se log RR = sqrt(1/3+...

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Statistical test for n x m contingency tables
4 votes

You can use multinom from nnet package for multinomial regression. Post-hoc tests you can use linearHypothesis from car package. You can conduct test of independence using linearHypothesis (Wald test)...

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Separating two populations from the sample
3 votes

For data in IQR range you should use truncated normal distribution (for example R package gamlss.tr) to estimate parameters of this distribution. Another approach is using mixture models with 2 or 3 ...

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How to fit a negative binomial distribution in R while incorporating censoring
2 votes

You can try gamlss.cens package.

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Correct spelling (capitalization, italicization, hyphenation) of "p-value"?
2 votes

P value from theoretical point of view is some realization of random variable. There is some standard (in probability) to use upper case letters for random variables and lower case for realizations. ...

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Using mixed effects modelling to estimate and compare variability
1 votes

You can calculate SD for each person and its standard error (for example using bootstrap). Then you can use rmeta package to do analysis. I think you should use some transformation of SD for example ...

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How to aggregate and merge these two data.frames?
0 votes

Answer to Goal 1: aggregate(. ~ Currency, data=subset(c,select=c("Currency", names(sapply(c,is.numeric)))),sum)

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Group differences on a five point Likert item
0 votes

Proportional odds ratio model is better then t-test for Likert item scale.

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What is the interpretation/meaning of confidence intervals in misspecified models?
0 votes

The answer depends on the degree of misspecification and sample size. In small and moderate samples simplified model will fit (in most cases) better to data then the true model. In moderate and large ...

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