There are 10 tickets in the box, 3 of them are winning. find the probability that you take one ticket from the box and it will be winning ticket, then you take second ticket and it will be also winning ticket. taken ticket is not returned back to the box. hint: p(a and b.= p(a)×p(b)

In a test for esp (extrasensory perception), a subject is told that cards only the experimenter can see contain either a star, a circle, a wave, or a square. as the experimenter looks at each of 20 cards in turn, the subject names the shape on the card. a subject who is just guessing has probability 0.25 of guessing correctly on each card. a. the count of correct guesses in 20 cards has a binomial distribution. what are n and p? b. what is the mean number of correct guesses in 20 cards for subjects who are just guessing? c. what is the probability of exactly 5 correct guesses in 20 cards if a subject is just guessing?