The average time taken to complete an exam, X, follows a normal probability distribution with mean = 60 minutes and standard deviation 30 minutes. What is the probability that a randomly chosen student will take at least an hour to complete the exam?
a. 0.1587
b. 0.5000
c. 0.8413
d. 0.9772
Q. 2The distinction between a sampling distribution and a confidence interval is:
a. A confidence interval gives possible values for a sample statistic when the population parameter is assumed known, while a sampling distribution gives possible values for a population parameter when only a single value of a sample statistic is known.
b. A sampling distribution gives possible values for a sample statistic when the population parameter is assumed known, while a confidence interval gives possible values for a population parameter when only a single value of a sample statistic is known.
c. Sampling distributions exist only for situations involving means, while confidence intervals can be computed for situations involving means and proportions.
d. Confidence intervals exist only for situations involving means, while sampling distributions can be computed for situations involving means and proportions.
Q. 3The average time taken to complete an exam, X, follows a normal probability distribution with mean = 60 minutes and standard deviation 30 minutes. What is the probability that a randomly chosen student will complete the exam in 30 minutes or less?
a. 0.1587
b. 0.5000
c. 0.8413
d. 0.9772
Q. 4Which of the following helps determine the standard error for a confidence interval for a mean?
a. The sample size(s).
b. The sample estimate.
c. The true value of the population parameter.
d. The confidence level.
Q. 5Weights of females have approximately a normal distribution with mean 135 lbs. and standard deviation 20 lbs. Allison weighs 145 lbs. What is the z-score for her weight?
a. 10
b. 1.50
c. 0.50
d. 0.20
Q. 6For each study, decide if the two samples are independent samples or paired samples. A group of 50 students had their blood pressures measured before and after watching a movie containing violence. The mean blood pressure before the movie was compared with the mean pressure after the movie.
a. Independent samples
b. Paired samples
Q. 7Scores on an achievement test had an average of 70 and a standard deviation of 10 . Serena's score was 85 . Assuming the scores have approximately a normal distribution, about what proportion of students scored lower than Serena?
a. 0.93
b. 0.07
c. 0.84
d. 0.68
Q. 8For each study, decide if the two samples are independent samples or paired samples. A group of 100 students were randomly assigned to receive vitamin C (50 students) or a placebo (50 students). The groups were followed for 2 weeks and the proportions of students with colds were compared.
a. Independent samples
b. Paired samples
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