BUS 223 Lecture Notes - Lecture 14: Confidence Interval, Standard Deviation
25 Jun 2018
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STUDENT’S t DISTRIBUTION
1. A survey of 16 taxi drivers found that the average tip they received is $1.40 with a
standard deviation of 80 cents. Find a 95% confidence interval for estimating the
average amount of money that a taxi driver receives as a tip.
2. A survey of the hospital records of 25 randomly selected patients suffering from a
particular disease indicated that the average length of stay in a hospital is 10 days
with a standard deviation of 2.1 days. Find the 99% confidence interval for
estimating the mean length of stay in a hospital.
3. A music teacher asks six randomly selected students how many hours a week
each practices the guitar. The mean was 10 hours with a standard deviation of
3.74 hours. Find the 90% confidence interval for the average length of time a
student practices playing the guitar.
4. It is claimed that the average annual salary of a police officer in Bolton is
$29,761. A random sample of 16 police officers reveals an average salary of
$29,023 with a standard deviation of $946. Using a 5% level of significance, can
we conclude that the average salary is less than $29,761?
5. Government officials claim that a call to the 911 emergency number brings an
ambulance in an average of 5.1 minutes. Hospital officials claim that the response
time is less since they upgraded the systems. A sample of 10 calls showed an
average response time of 4.6 minutes with a standard deviation of 1.2 minutes.
Does this indicate an improvement in service at the 1% level of significance?
6. A psychologist claims that rats require an average of 10 minutes to find their way
through a maze. Seven rats require 11 minutes with a standard deviation of 3.6
minutes. Using a 5% level of significance can we conclude that it does not take 10
minutes for a rat to find its way through a maze?
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Document Summary
Student s t distribution: a survey of 16 taxi drivers found that the average tip they received is . 40 with a standard deviation of 80 cents. Find the 99% confidence interval for estimating the mean length of stay in a hospital: a music teacher asks six randomly selected students how many hours a week each practices the guitar. The mean was 10 hours with a standard deviation of. Find the 90% confidence interval for the average length of time a student practices playing the guitar: it is claimed that the average annual salary of a police officer in bolton is. A random sample of 16 police officers reveals an average salary of. Using a 5% level of significance, can we conclude that the average salary is less than ,761: government officials claim that a call to the 911 emergency number brings an ambulance in an average of 5. 1 minutes.
