The principal at Riverside High School would like to estimate the mean length of time each day that it takes all the buses to arrive and unload the students.
How large a sample is needed if the principal would like to assert with 90 confidence that the sample mean is off by, at most, 7 minutes. Assume that s = 14 minutes based on previous studies. A) 11 B) 10 C) 12 D) 13
Q. 2Given events C and D with probabilities P(C) = 0.3, P(D) = 0.2, and P(C and D) = 0.1, are C and D independent?
A) no B) yes C) cannot be determined
Q. 3Of the 3800 students at a college, 280 are mature students. 50 students are selected at random from the 3800 students at the college and asked to participate in a survey.
The questions in the survey relate to the students need for financial assistance. The random variable X represents the number of mature students in the sample. A) hypergeometric; N = 3800, n = 50, k = 280, x = 0, 1, 2, . . . , 50
B) hypergeometric; N = 3800, n = 280, k = 50, x = 0, 1, 2, . . . , 50
C) hypergeometric; N = 3800, n = 50, k = 280, x = 0, 1, 2, . . . , 280
D) not hypergeometric
Q. 4Assuming that all conditions are met to approximate a binomial probability distribution with the standard normal distribution, then to compute P(x 23 ) from the binomial distribution we must compute as the normal approximation.
A) P(x 23.5 ) B) P(x 23.5 ) C) P(x 22.9 ) D) P(x 23.1 )
Q. 5Find the critical value from the Studentized range distribution for H0: 1 = 2 = 3 = 4 = 5, with n = 18 at = 0.01.
A) 5.727 B) 5.404 C) 5.379 D) 5.094
Q. 6The grade point averages for 10 randomly selected students in an algebra class with 125 students are listed below. What is the effect on the width of the confidence interval if the sample size is increased to 20?
2.0 3.2 1.8 2.9 0.9 4.0 3.3 2.9 3.6 0.8
A) The width decreases.
B) The width increases.
C) The width remains the same.
D) It is impossible to tell without more information.
Q. 7A medical journal published the results of an experiment on anxiety. The experiment investigated the effects of a controversial new therapy for anxiety.
Researchers measured the anxiety levels of 65 adult women who suffer moderate conditions of the disorder. After the therapy, the researchers again measured the womens anxiety levels. The differences between the the pre- and post-therapy anxiety levels were reported. How many levels does the treatment have in this experiment? A) 2 (pre- and post-therapy)
B) 1 (therapy)
C) 65 (the adult women who suffer from anxiety)
D) 130 (the adult women who suffer from anxiety measured pre- and post-therapy)
Q. 8A doctor at a local hospital is interested in estimating the birth weight of infants.
How large a sample must she select if she desires to be 90 confident that her estimate is within 2 ounces of the true mean? Assume that s = 5 ounces based on earlier studies. A) 17 B) 16 C) 5 D) 4
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