A simple random sample of 33 owners of a certain model of automobile were asked how many
defects had to be corrected within the first six months of ownership. The sample showed an
average of 3.7 defects, with a sample standard deviation of 1.8 defects.
The pulse rates of 32 students are taken before and after the announcement of a surprise quiz.
The average increase in pulse rates is found to be 24.2 beats per minute (b/m). From previous
studies, the population standard deviation is known to be 5.15 b/m
1. In a large industry where well over 100,000 employees are represented by a single
union, a simple random sample of 100 union members finds that 57% of those in the
sample intend to vote for the new labor contract. What is the 99% confidence interval fo
1. Suppose a student measuring the boiling temperature of 6 different liquids calculates the
sample mean to be 101.82 (in degrees Celsius). Boiling temperatures are normally
distributed. If the student knows that the population standard deviation for this
1. Define the following terms: Estimator, Estimate, Point Estimate, and Interval Estimate.
An estimator is the sample statistic which is used to estimate a parameter.
An estimate is the numerical value of the estimator that is used.
A point estimate is a
A polling organization wants to estimate the proportion of voters who today say
they would vote for candidate x in the next election. They want to maximum error
to be only one percentage point, .01, with a probability of 0.95. At this early stage,
1. The manager of a tire manufacturing company wants to determine the proportion of tires
that are flawed. The manager selects a random sample of 200 tires for analysis and finds
that 35 tires contain some flaw. What is the confidence interval estimate fo
1. Given the following confidence levels, fill in the table below:
= X Z X
= 21.86 to 26.54
1. Suppose that auditing procedures require you to estimate the population proportion of
sales invoices with errors within 0.07 of the true population proportion. Studies done in
the past indicate a population proportion of 0.15. What is the sample size n
In a simple random sample of 31 homes in the Bronx, it was found that the average annual
usage of heating oil was 1122.75 gallons with a standard deviation of 295.72 gallons. Based on
these data, there is 95% confidence that the mean annual usage of heati