An unconfined compression test was performed to determine the average strength of concrete cylinders (in psi). it is believed that the strength is approximately normally distributed with a standard deviation of 196 psi. a sample of 50 concrete cylinders was taken, and it was found that the average strength was 2500 psi. find a 92% confidence interval for the true average strength of the concrete.

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?