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Unit Test

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The proportions of multiple samples of registered voters who vote are normally distributed, with a mean proportion of 0.38 and a standard deviation of 0.0485. What is the probability that a sample chosen at random has a proportion of registered voters who vote between 0.37 and 0.39? Use the portion of the standard normal table below to help answer the question.
17%
A supervisor finds the mean number of miles that the employees in a department live from work. He finds mc022-1.jpg and mc022-2.jpg. Which statement must be true?
z37 is between 2 and 3 standard deviations of the mean.
What is the formula for margin of error?
ME=z×s over √n
The times of all 15 year olds who run a certain race are approximately normally distributed with a given mean µ= 18 sec and standard deviation σ= 1.2 sec. What percentage of the runners have times less than 14.4 sec?
0.15%
Opal is collecting data on water levels in different parts of town. She notices that her sample data has a low-value outlier. Which statement must be true?
Removing the outlier will decrease the spread of the graph of the data set.
A scientist calculated the mean and standard deviation of a data set to be µ=120 and σ=9. She then found that she was missing one data value from the set. She knows that the missing data value was exactly 3 standard deviations away from the mean. What was the missing data value?
147
When finding the margin of error for the mean of a normally distributed population from a sample, what is α, assuming a confidence level of 74%?
0.26
Which set of population data is the least dispersed from its mean?
6, 2, 2, 2
The life spans of a computer manufacturer's hard drives are normally distributed, with a mean of 3 years 6 months and a standard deviation of 9 months. What is the probability of a randomly selected hard drive from the company lasting between 2 years 3 months and 3 years 3 months? Use the portion of the standard normal table below to help answer the question.
32%
The set of life spans of an appliance is normally distributed with a mean µ= 48 months and a standard deviation σ= 8 months. What is the life span of an appliance that has a z-score of -3?
24 months
A normal distribution of data has a mean of 90 and a standard deviation of 18. What is the approximate z-score for the value 64?
-1.4
The grades of a science test are normally distributed. Thanh finds that his grade on the test has a z-score of -2.5. Which statement must be true?
Thanh's grade is 2.5 standard deviations below the mean of the test grades.
The times taken to assemble a clock at a factory are approximately normally distributed with a given mean µ= 3 hr and standard deviation σ = 0.5 hr. What percentage of the times are between 2 hr and 4 hr?
95%
A simple random sample of size n is drawn from a normally distributed population, and the mean of the sample is x, while the standard deviation is s. What is the 90% confidence interval for the population mean? Use the table below to help you answer the question.
x=1.645×s over √n
A city's annual rainfall totals are normally distributed, and the probability that the city gets more than 43.2 inches of rain in a year is given by P(z≥1.5)=0.0668. If the standard deviation of the city's yearly rainfall totals is 1.8 inches, what is the city's mean annual rainfall?
40.5 inches
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