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 Oct 7 comment Probability given a mean and standard deviation of a random variable @DilipSarwate sorry, i take that back. I think i had assumed the distribution to be normal... Oct 7 answered Probability given a mean and standard deviation of a random variable Oct 7 comment Why can we use poisson distribution in this case? the n is very small!! are you sure $$$\frac{n(n-1)\ldots(n-k+1)}{n^n} \approx 1$$$? because (by looking at how it's derived) the denominator is $k!$ Oct 6 asked Why can we use poisson distribution in this case? the n is very small!! Oct 6 comment Is it possible to do this Poisson problem in Binomial? ive added the second part of the problem, can you help convert that into binomial? Thank you very much!! Oct 6 revised Is it possible to do this Poisson problem in Binomial? added 97 characters in body Oct 6 comment Is it possible to do this Poisson problem in Binomial? i got it! going back to question (a) i tried to find the prob $(\frac{364}{365})^{80000}$ why is that wrong? Oct 6 comment Is it possible to do this Poisson problem in Binomial? Hi Henry, question (b) asks (b) both partners celebrated their birthday on the same day of the year. the solution says The probability that an arbitrary couple were born on the same day of the year is $\frac{1}{365}$. why is that? why isn't it the same $\frac{1}{365^2}$ Oct 6 revised Is it possible to do this Poisson problem in Binomial? added 4 characters in body Oct 6 asked Is it possible to do this Poisson problem in Binomial? Oct 5 accepted Performing hypothesis test for the difference of population means: paired comparisons Oct 5 comment Performing hypothesis test for the difference of population means: paired comparisons @MichaelChernick to summarize, I cannot use the 2 sample independent t test because there's a strong correlation (or dependence) between the two variables. The experimental design is better suited with paried comparisons. correct? Oct 4 comment Why does negative binomial random variable uses ${n-1 \choose r-1}$ instead of ${n \choose r}$ as coefficient? This is a good answer, Thank you! however what I don't understand is that with ${n-1 \choose r-1}$ aren't we skipping the last trial? It's a guaranteed success, but we shouldn't ignore it Oct 4 comment Why does negative binomial random variable uses ${n-1 \choose r-1}$ instead of ${n \choose r}$ as coefficient? i understand r-1 success in n-1 trial part, but the last trial must be a success then that makes it ${n \choose r}$... if we do ${n-1 \choose r-1}$ we lose the last trial! Oct 4 comment Performing hypothesis test for the difference of population means: paired comparisons @MichaelChernick why do you think using the formula for 2 sample t test is incorrect in this scenario? I think we can use it because has been used to determine difference of population means. my thoughts are, if anything, this and the paired t test should come to the same conclusion... Oct 4 asked Why does negative binomial random variable uses ${n-1 \choose r-1}$ instead of ${n \choose r}$ as coefficient? Oct 4 comment Performing hypothesis test for the difference of population means: paired comparisons @MichaelChernick yes, thank you for answering, but it looks like you have discussed the topic in CV, but Im wondering what is CV... Oct 4 comment Performing hypothesis test for the difference of population means: paired comparisons Yes! an answer!!! Michael you're AWSOME!!!! Oct 4 comment Performing hypothesis test for the difference of population means: paired comparisons thanks for answering michael, what exactly is a CV? Oct 3 revised Performing hypothesis test for the difference of population means: paired comparisons edited title