STA questions and correct answer

STA questions and correct answers A tennis player makes a successful first serve 51% of the time. If she serves 9 times, what is the probability that she gets exactly 3 successful first serves in? Assume that each serve is independent of the others. - ANSWERS .154 A survey showed that 81% of adults need correction (eyeglasses, contacts, surgery, etc.) for their eyesight. If 16 adults are randomly selected, find the probability that no more than 1 of them need correction for their eyesight. Is 1 a significantly low number of adults requiring eyesight correction? A. The probability that no more than 1 of the 16 adults require eyesight correction is - ANSWERS a. .0000 b. Yes, because the probability of this occurring is small. Based on a Comcast survey, there is a 0.8 probability that a randomly selected adult will watch prime-time TV live, instead of online, on DVR, etc. Assume that seven adults are randomly selected. Find the probability that fewer than three of the selected adults watch prime-time live. - ANSWERS .00467 Twenty percent of adults in a particular community have at least a bachelor's degree. Suppose x is a binomial random variable that counts the number of adults with at least a bachelor's degree in a random sample of 100 adults from the community. If you are using a calculator with the binompdf and binomcdf commands, which of the following is the most efficient way to calculate the probability that more than 60 adults have a bachelor's degree, P(x60)? - ANSWERS p(x60)=1- binomcdf(100,.20,60) Determine whether the following value is a continuous random variable, discrete random variable, or not a random variable. a. The number of home runs in a baseball game b. The usual mode of transportation of people in City Upper A c. The number of statistics students now doing their homework d. The number of free dash throw attempts before the first shot is missed e. The number of people with blood type Upper B in a random sample of 39 people f. The number of textbook authors now eating a meal - ANSWERS a. discrete b. not a random variable c. discrete d. discrete e. discrete f. discrete Twenty percent of adults in a particular community have at least a bachelor's degree. Suppose x is a binomial random variable that counts the number of adults with at least a bachelor's degree in a random sample of 100 adults from the community. Which of the following probability statements indicates the probability that at least 30 adults have at least a bachelor's degree? - ANSWERS p(x great than or equal to 30) Mars, Inc. claims that 20% of its M&M plain candies are orange. A sample of 100 such candies is randomly selected. Find the mean and standard deviation for the number of orange candies in such groups of 100. - ANSWERS Mean:20, Standard dev:4.0 A test consists of 10 true/false questions. To pass the test a student must answer at least 6 questions correctly. If a student guesses on each question, what is the probability that the student will pass the test? Round to three decimal places. - ANSWERS .377 What does it mean to say that the trials in a binomial experiment are independent of each other? - ANSWERS The outcome of one trial does not affect the outcomes of the other trials. A die is rolled nine times and the number of times that two shows on the upper face is counted. If this experiment is repeated many times, find the mean for the number of twos. - ANSWERS 1.5 two