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 Oct6 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? Oct6 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 $\frac{1}{365^2}$ Oct5 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? Oct4 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 Oct4 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! Oct4 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... Oct4 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... Oct4 comment Performing hypothesis test for the difference of population means: paired comparisons Yes! an answer!!! Michael you're AWSOME!!!! Oct4 comment Performing hypothesis test for the difference of population means: paired comparisons thanks for answering michael, what exactly is a CV? Sep30 comment How do we identify a probability problem as a conditional probability problem? @DilipSarwate minor math latex error Sep30 comment How do we identify a probability problem as a conditional probability problem? @DilipSarwate if they had used the keyword "Given" it would've been much easier, but here it doesn't use the keyword "Given". What other clues should i look for? Sep24 comment Solving an equation with three quadratic radicals in the set of real numbers 2 seems to work... Sep24 comment Probability in flipping a coin @did the answer is accepted, when i unaccepted the answer, I added questions in the comment beneath the answer, and Jean provided answers to my questions, so i reaccepted his answer. Sep23 comment Confusion on the meaning of confidence interval it seems quite reasonable that they would "cancel" out because sometime we'd get a sample mean higher than the true mean sometimes lower, but is there a formal explanation as to how they cancel(usually should be some proof or explanation) for this, if not "convenient", cancellation. Sep22 comment Confusion on the meaning of confidence interval i see, you want to be precise. but can you explain why is the area under the curve to the left of 72.1 is less than the area under the curve to the right of 72.1 in the graph above? Sep22 comment Confusion on the meaning of confidence interval but why is the area under the curve to the left of 72.1 less than the area under the curve to the right of 72.1 in the graph above? Sep22 comment Confusion on the meaning of confidence interval we should be able to assume the distribution is normal because of Central Limit Theorem, and in this case $n$ >30 Sep22 comment Probability in flipping a coin shouldn't the answer be $1-p-p^2-p^3-p^4$ because $1-p^4$ only excluded the possibility that all of the first 4 flips are H, we can also have HTHHH, HHTHHH, HHHTHHH, therefore those probabilities need to be subtracted as well. Sep22 comment Probability in flipping a coin ok yes, you're correct. ill think about it a little bit more Sep22 comment Probability in flipping a coin your answer is very insightful, but after reading them, I tend to side with the answer $1-p$ simply because we can have any gibberish after the first flip, for example, THTHTHTTH, if we want to form HHHH, we must have HHH, and because we have ensured that the first roll is not an H, we will eventually have THHH, in my suggested gibberish example, it would turn out to be THTHTHTTHHH, there we have THHH before HHHH. So $1-p$ excludes the possibility that on the first flip, we have a H, there's the answer we're looking for.