Recent content by AngleWyrm

  1. AngleWyrm

    Causality and independence

    katxt said: We can express this probability as P( X has had a motor accident | X is in hospital). The condition clearly happened after the event. If P( accident | hospital) > P(accident) then we have a measured judgement people who've had accidents are more frequently found in hospitals. The |...
  2. AngleWyrm

    Causality and independence

    If P(cancer | smoker) > P(cancer), cancer is more frequent among smokers, then can we say smoker came before cancer, and shows a causal relationship? Here's the rub I've seen so far, which seems to me Simpson's Paradox: It may also be the case P(smoker | cancer) > P(smoker), smokers are more...
  3. AngleWyrm

    Causality and independence

    Do you agree that P(A|B) is a mathematical model of dependence? That is to say P(A) given P(B) states a before/after relationship, and a causality of B effecting A?
  4. AngleWyrm

    Causality and independence

    You appear to be discussing something that isn't the draw of a card A followed by the draw of a card B. It looks like you might be talking about a strategy game where two players hold more than one card each, and are choosing to play cards from their hands. Do you agree the cards a player drew...
  5. AngleWyrm

    Causality and independence

    Pearson's chi squared test for independence Tests of Independence If A and B are independent then P(A AND B) = P(A)P(B)
  6. AngleWyrm

    Causality and independence

    Player 1 draws a card from a deck, and then player 2 draws a card. This is a causal relationship: Player 1's draw occurred before player 2's draw, and had an effect on what player 2 could draw. The player's hands are not independent events. The claim event A did something to effect the outcome...
  7. AngleWyrm

    Testing if a sample came from a population

    Yes that's a good match: Pearson's Chi squared test of independence Calculators for finding decision value, and test statistic
  8. AngleWyrm

    Testing if a sample came from a population

    The stated claim is event A and event B are independent, with probabilities P(A) = 0.90 and P(B) = 0.20 Given a set of samples, how can we measure the certainty they were drawn from that population? With two events, there are four possible outcomes to a test, {A and B, A and not B, not A and B...
  9. AngleWyrm

    Creating a scale with dichotomous and continuous items

    Check out Principal Component Analysis
  10. AngleWyrm

    How to test this scenario?

    So you have a population of all people, and four samples drawn from that population, called red, brown, blonde, and black. Since this is a problem where sample sizes differ, we should use a z-score that takes sample size into account. Normal z score = (observation - average)/(standard...
  11. AngleWyrm

    Cross-national comparison best methodology and research questions advice

    I hypothesize attitudes toward justice correlate with annual wages. Does the survey taker earn more than the median for 1 person? More than ten people? Less than 1/5th?
  12. AngleWyrm

    Chance performance in a binary response task

    80/100 = 4/5 of answers are true, 1/5 of answers are false. If the subject knows this, then their best guessing strategy is to guess true 4/5 of the time and false 1/5 of the time.
  13. AngleWyrm

    A coincidence isn't that unlikely?

    Gambler's Fallacy
  14. AngleWyrm

    A coincidence isn't that unlikely?

    The Gambler's Fallacy is a trick of memory, where the observer considers what has been observed but doesn't remember what hasn't taken place.
  15. AngleWyrm

    Question Regarding Standard Deviation of Rate Vs. Time

    Mean for the rate in ml/s wasn't calculated in the original, so I madea copy and added it (blue outlined cells) I also agree the time to complete the fill operation is a better measure. The average speed in ml/sec varies considerably between pumps, and so a small variance in the smallest...