



 
Hi Katrina, 1) A chairperson can be selected in 20 different ways, each of the 20 people could be selected. Once a chairperson has been selected there are 19 ways to choose an assistant. Thus there are 20 * 19 ways to select a chairperson and an assistant. 2) This is a binomial probability question with n = 10, p = 1/2 and X the number of questions the student gets correct. You are asked to find Pr(X > 7) 3) You are given a normal random variable X with mean 68 inches and standard deviation 3 inches. From a random sample of size n = 25 you are asked to find Pr(68.5 < Xbar < 72). Xbar is also a normal random variable with mean 68 inches but its standard deviation is 3/root(25). Convert the probability statement to a statement concerning the standard normal distribution and look up the probabilities in the standard normal table. I hope this helps,  


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