In a random sample of 44 Democrats from one city, 13 approved of the mayor's performance. In a random sample of 53 Republicans from the city, 31 approved of the mayor's performance.
Find a 90 confidence interval for the difference between the proportions of Democrats and Republicans who approve of the mayor's performance.
A) 0.136 to 0.455 B) 0.105 to 0.485 C) 0.106 to 0.485 D) -0.448 to -0.131
Q. 2A farmer wishes to test the effects of a new fertilizer on her tomato yield. She has four equal-sized plots of land-- one with sandy soil, one with rocky soil, one with clay-rich soil, and one with average soil.
She divides each of the four plots into three equal-sized portions and randomly labels them A, B, and C. The four A portions of land are treated with her old fertilizer. The four B portions are treated with the new fertilizer, and the four C's are treated with no fertilizer. At harvest time, the tomato yield is recorded for each section of land. Identify the experimental units.
A) the three types of fertilizer B) the four types of soil
C) the tomato yield at harvest time D) the tomato plants on the various plots of land
Q. 3The tread life of a particular brand of tire is a random variable best described by a normal distribution with a mean of 60,000 miles and a standard deviation of 2900 miles.
What is the probability a particular tire of this brand will last longer than 57,100 miles?
A) 0.2266 B) 0.1587 C) 0.7266 D) 0.8413
Q. 4A mayoral election race is tightly contested. In a random sample of 1200 likely voters, 636 said that they were planning to vote for the current mayor. Based on this sample, would you claim that the mayor will win a majority of the votes? Explain.
What will be an ideal response?
Q. 5Suppose that you know the area under the standard normal curve between 1 and 3 and the area under the standard normal curve to the left of 3.
Without further consulting a table of areas, how could you find the area under the standard normal curve to the left of 1? Explain your reasoning by using a sketch of the standard normal curve.
Q. 6A television station claims that the amount of advertising per hour of broadcast time has an average of 17 minutes and a standard deviation equal to 1.1 minutes.
You watch the station for 1 hour, at a randomly selected time, and carefully observe that the amount of advertising time is equal to 9 minutes. Calculate the z-score for this amount of advertising time.
A) z = -7.27 B) z = 7.27 C) z = 0.46 D) z = -0.46
Q. 7A farmer wishes to test the effects of a new fertilizer on her potato yield. She has four equal-sized plots of land-- one with sandy soil, one with rocky soil, one with clay-rich soil, and one with average soil.
She divides each of the four plots into three equal-sized portions and randomly labels them A, B, and C. The four A portions of land are treated with her old fertilizer. The four B portions are treated with the new fertilizer, and the four C's are treated with no fertilizer. At harvest time, the potato yield is recorded for each section of land. What type of experimental design is this?
A) matched-pairs design B) completely randomized design
C) randomized block design D) double-blind design
Quick Reply
