Recent content by Hans Rudel

  1. H

    Sampling methods, which is more appropriate?

    I have been collecting data on the temperature in an experiment for the last couple months, and I'm interested in the rate of temperate changes. The total amount of data is extremely large, and takes a long time to process, even using multi-threaded code. Currently I'm doing option 1, but I'm...
  2. H

    Sample distribution of means and the minimum number of samples/population size

    Hi, Im having some issues with 2 things, and would appreciate it if someone could clear things up. (1) Ive read that the mean of "the sampling distribution of means" is the same as the "populations" mean. To construct the sampling distribution of means, i need to take X * number of...
  3. H

    Confidence interval, does a difference in sample size affect comparison of results?

    I have a time series and im trying to calculate the confidence interval (95%) for the time taken to experience a +ive or -ive move of X%. I would like to do this for several X's, ie 10%, 30%, 50%. Am i correct in assuming that i should try and ensure that each level of X% has the same/similar...
  4. H

    lottery tickets, better to buy all for one game or play X number of games

    Im wondering which would be better. Im assuming the following, chance of winning = 10,000 for a particular ticket. So if i bought 10 tickets, the probability of winning one would be 1/1,000 2nd scenario, if i bout all 10 for one particular game, is there a difference? I originally used a...
  5. H

    Genetic algorithm, confusion with selection/reproduction step.

    Hi, im a little confused with the selection/reproduction step in genetic algorithms. Im aware that the initial population has several hundred in it. That the fitness function is used to select a certain number of the possible solutions for cross over/mutation. What i dont get is how the...
  6. H

    Binomial Distribution, 150 tosses of fair coin, P(40%<= X <=50%)

    Hi, im getting the wrong answer for the following question and not sure why. (Question) A fair coin is tossed 150 times. Find the probability that between 40% and 50% (inclusive) of the tosses will result in heads. (I know its possible to do this proportions but i prefer to do it with...
  7. H

    Continuity correction for proportions

    Could someone please explain how to calc the continuity correction for a proportion ie P(X >= 0.03) I understand that if this was not a proportion P(X >= 3) -> P(X > 2.5) but i dont see how im suppose to do this for a proportion. Any help would be appreciated
  8. H

    Central limit theorem, confusion over sample size.

    Good morning, Im having some issues getting my head around the sample size of the central limit theorem. Eg Thirty random observation are taken from each of the following distributions and the sample mean is calculated. Find the probability that the sample mean exceeds 5 given that X is the...
  9. H

    Expected value

    Could someone please explain the following? A guy and a girl play a game where they roll a dice. If the guy rolls an even number, the girl pays him that amount. If he rolls an odd number he pays her that amount. The expected value is supposedly $0.5. ie mean of -1+2-3+4-5+6 but if i...
  10. H

    Poisson or Binomial

    Hi, im trying to make sure i have the difference between when to use Binomial and Poisson distributions firmly understood. Regarding the following question, im assuming its a Binomial since its possible to determine p and q even though a rate is specified? Question) If a baseball batter hit 4...
  11. H

    Poisson distribution, no call on 3 days out of 5 between 10.00am and 10.10am

    Hi, im having some issues with the following question. Question) A sales manager receives 6 phone calls on average between 9.30am and 10.30am on a weekday. Find the probability that during a 5 day working week, there will be exactly 3 days on which she receives no calls between 10am and...
  12. H

    E(X), bag with 6 red and 5 black balls, X = number of red balls

    A bag contains 5 black and 6 red balls. Two counters are drawn, one at a time, and not replaced. Let X be "the number of red counters drawn". Find E(X). ive drawn up a tree diagram which im assuming is correct EDIT: Below is the corrected tree diagram, as eagle eye Dason had spotted a mistake...
  13. H

    2 four sided dice, probability of 1 dice = 3, sum = even

    [Question] 2 four tetrahedral dice with sides, 1,2,3,4. the two dice are thrown, what is the probability that given the first dice is a 3, the sum of the 2 dices will be an even number. This has had me stumped for about 30mins. im assuming i should be using P(A|B) = P(A&B)/P(B) where...
  14. H

    Only one of two events occurs

    P(A) = 8/15 P(B) = 1/3 P(A|B) = 1/5 (Question) calculate the probability that only one event occurs. i have already calculated that the P(A&B) = P(B) x P(A|B) = 1/15 P(A'&B') = 0.2 from the following P(AorB) = (P(A) + P(B) - (PA&B) so 1 - P(AorB) = P(A'&B') i thought the answer to the...
  15. H

    Lines of regression

    Im little confused with the following. there are 12 patients, each is assigned assigned an index I when first administered depending on the severity of their symptoms. Each then administered a drug and 30 days later they are given another index F which will hopefully be lower than I if they...