# distribution

1. ### Estimating values from kurtosis and skewness

If I know the size of a population, the number of categories/labels, and the skewness and kurtosis of the distribution, is it possible to estimate the number of items which fall into each category? For example, given the data set: category A: 11 category B: 13 category C: 15 category D...
2. ### Survey data and STATA svy functions

Hi! I'm working with a large dataset which is heavily weighted. I need to produce the distribution of weights by key variables in our dataset (region, race, etc). This may be an elementary question, but to produce the distributions do I use the "summarize" and "tab" functions, or do I need to...
3. ### Sum of independent beta-Bernoulli random variables

I'm looking for the distribution of the sum of independent beta-Bernoulli random variables, that is Bernoulli random variables with beta-distributed parameters, x_i ~ Bern(p_i) with p_i ~ beta(alpha,beta) (same alpha and beta, of course). I guess one can work with convolutions or characteristic...
4. ### Uniform and Independent Probability (Simple Problem)

Hey there, I have a quick question. The problem: 3 numbers, say X, Y, and Z are chosen from a set of numbers (1 to n) where n is greater or equal to 1, in a uniform and independent manner. Question 1 What's the chance that all these three numbers take on the same value, i.e. X=Y=Z...
5. ### sample distribution of residuals

Find the sample distribution of the residual r = y - XBhat under normal regression model assumptions.* * I think this means to assume errors are indepedent, have mean 0 and variance sigma squared, are are normally distributed. Please help! Are residuals not just realizations of the errors and...
6. ### How do you calculate Skewness? Not the simple case...

Hello, To begin with I would like you to take into account that I'm not a maths genius, but I understand maths to a good degree. My question is how do you find skewness in univariate probability distributions that are both asymmetric and multimodal? I have two columns of raw data: x - Plotted...
7. ### Is my variable count or measurement and what statistical model would be best?

I am trying to assess the fine-scale spatial distribution of tadpoles along a depth gradient in relation to abiotic and biotic factors -- and am having great difficulty in determining the best statistical test (Chi square VS ANOVA) to use BECAUSE I cannot determine what kind of data I have...
8. ### Spatial distribution of points

Hi, I'm working on spatial distribution of points (being location of volcanoes). I found so far a linear correlation between the mean distance between nearest neighbours and the density in a semi-log plot. I'm looking for ideas and ways to study these fields of points/volcanoes. Cheers...
9. ### Proof that the cumulative distribution function doesn't need to be left-contiguous

If we take (X<=x) = ]-Inf, x] = /intersect_n^inf {]-Inf, x+(1/n)]}, we have that the cumulative distribution function would be F(x) = P(X<=x) = lim_n^inf P(X<=x+1/n), which proofs that the cumulative distribution function needs to be right-contiguous. If I do a similar trick: take (X<=x) =...
10. ### Normal Probability Distribution

In 2010, the population of SAT scores were normally distributed with a mean of 1020 (reading and math only) and a standard deviation of 200. The NCAA requires Division I athletes to score at least 820 to compete the first year. A random sample of 4 students is gathered. What is the probability...
11. ### Poisson Distribution

What is the probability there are at least 24 accidents at the intersection in a year if the mean number of accidents per month is 2.2? (answer=0.693) I keep getting 0.706, which is close to the listed answer, but I'm not sure if it is correct. My attempt: P(X≥24) = P(X>24)+P(X=24) =...