## Your Results:Math 203 - Practice, Exam 2

Question 1: Score 5/5
 Suppose that the heights of American women form a normal distribution whose mean is 65.9 inches and whose standard deviation is 1.8 inches. Then the middle 95.0 % of women's heights in inches are between what two numbers? Enter the smaller number in (a). Your answer should be a number with no units. Enter the larger number in (b). Your answer should be a number with no units.
 (a) 65.9-2*1.8 (b) 65.9+2*1.8

Question 2: Score 5/5
 A raffle ticket costs \$4. The probability of winning the \$170 first prize is 1/86 and the probability of winning the \$33 second prize is 1/40. What are the mean winnings in dollars for one play, taking into account the \$4 cost of the ticket? (Your answer should be a number with no units, accurate to within 0.01.)
 Ans: (1/86)*(170-4)+(1/40)*(33-4)+(1-(1/86)-(1/40))*(0-4)

Question 3: Score 5/5
 You wish to survey the students at UNL to determine their feelings about the quality of services at the Union. Which of the following sampling designs is best for avoiding bias?
 Your Answer: Obtain a list of student names from the registrar and select 250 names at random to contact.

Question 4: Score 5/5
 An owner of a local fast-food restaurant decided to determine if her customers would appreciate the addition of fat-free items to the menu. A survey of 75 people at her restaurant found 30 in favor of the new fat-free menu items. In this survey the population consists of ______ and the sample consists of ______.
 Your Answer: An owner of a local fast-food restaurant decided to determine if her customers would appreciate the addition of fat-free items to the menu. A survey of 75 people at her restaurant found 30 in favor of the new fat-free menu items. In this survey the population consists of all people who eat at the restaurant and the sample consists of 75 surveyed people at the restaurant.

Question 5: Score 5/5
 Suppose that 41 % of all the guardrail posts are bad, and that 129 posts are selected at random. Give a 99.7% confidence interval for the percentage of bad posts in the sample. (Your answers should be accurate to within 1 percentage point.) Enter the lower end of your confidence interval in (a). (Omit the % sign from your answer.) Enter the upper end of your confidence interval in (b). (Omit the % sign from your answer.)
 (a) 41-3*sqrt((41/100)*((100-41)/100)/129)*100 (b) 41+3*sqrt((41/100)*((100-41)/100)/129)*100

Question 6: Score 5/5
 The following are the 22 lengths (in centimeters) of fish of a certain species caught on a fishing expedition: 40, 60, 43, 69, 36, 38, 41, 44, 31, 64, 70, 64, 66, 42, 67, 80, 42, 66, 50, 62, 58, 37. Write the five-number summary for this set of data. Your numbers should be listed from least to greatest.
 (a) 31 (b) 41 (c) (50+58)/2 (d) 66 (e) 80

Question 7: Score 5/5
 A recent study was done on the cost of making valves for government air conditioners. Nine price quotes were obtained from nine manufacturers: \$ 3000, \$ 2800, \$ 3400, \$ 1500, \$ 1100, \$ 4200, \$ 2600, \$ 2500, \$ 3600. It is known that the standard deviation of valve price is \$ 1100, and you should assume that the price distribution is normal. Find a 95% confidence interval for the mean price of valves in dollars. (Your answers should be accurate to within \$1.) Enter the lower end of your confidence interval in (a). (Omit the \$ symbol.) Enter the upper end of your confidence interval in (b). (Omit the \$ symbol.)
 (a) (30+28+34+15+11+42+26+25+36)*100/9-2*(1100/sqrt(9)) (b) (30+28+34+15+11+42+26+25+36)*100/9+2*(1100/sqrt(9))

Question 8: Score 5/5
 A couple has eleven children: Maureen, Renee, Florian, Kevin, Patrick, Colleen, Megan, Terence, Daniel, Erin, and Jonathan. A local contest randomly selects one of them to win a bicycle. In (a), enter the probability that the winner's first name has at least 6 letters. In (b), enter the probability that the winner's first name ends in "n" and has at least 6 letters. (Your answers should be accurate to within 0.01.)
 (a) (1+0+1+0+1+1+0+1+1+0+1)/11 (b) (1+0+1+0+0+1+0+0+0+0+1)/11