distribution

  1. S

    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...
  2. B

    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...
  3. A

    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...
  4. H

    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...
  5. A

    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...
  6. N

    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...
  7. R

    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) =...
  8. T

    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...
  9. T

    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) =...