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# Confidence Interval and Probability

4) A building developer has the opportunity to purchase several acres of land that is divided up into several lots for building single-family homes. It is known that the average sale price of all of the lots is \$80,000 and the standard deviation of the sale price is \$12,000. What can you say about the percentage of lots that have selling prices between \$56,000 and \$104,000?
a. approximately 95% of the selling prices lie in this interval
b. at most 25% of the selling prices lie in this interval
c. at least 75% of the selling prices lie in this interval
d. approximately 99.7% of the selling prices lie in this interval
e. none of these
Also,

6) One of the problems encountered by corporations in America is finding an adequate number of employees who want to move into management. Recent surveys of workers in America taken by the Department of Labor in Washington D. C. revealed that only 20% of employees would like to move into management and be the boss. Suppose that a random sample of 75 U.S. workers was taken and each person was asked whether or not they would like to move into management. Find the probability that at least 18 of the 75 sampled employees would like to move into management.