MATH 225N / MATH225N
WEEK 6 QUESTIONS AND ANSWERS
Question 1
A statistics professor recently graded final exams for students in her introductory statistics course. In a review of her grading, she found the mean score out of 100 points was a x¯=77, with a margin of error of 10.
Construct a ...
Question 1
A statistics professor recently graded final exams for students in her introductory statistics
course. In a review of her grading, she found the mean score out of 100 points was a x¯=77,
with a margin of error of 10.
Construct a confidence interval for the mean score (out of 100 points) on the final exam.
That is correct!
Answer: (67, 87)
Question 2
A random sample of adults were asked whether they prefer reading an e-book over a printed
book. The survey resulted in a sample proportion of p′=0.14, with a sampling standard
deviation of σp′=0.02, who
preferred reading an e-book.
Use the empirical rule to construct a 95% confidence interval for the true proportion of adults
who prefer e- books.
That is correct!
Answer: ( 0.10, 0.18)
Question 3
The pages per book in a library are normally distributed with an unknown population mean. A
random sample of books is taken and results in a 95% confidence interval of (237,293)
pages.
What is the correct interpretation of the 95% confidence interval?
We estimate with 95% confidence that the sample mean is between 237 and 293 pages.
Weisestimate
That correct! that 95% of the time a book is selected, there will be between 237 and
293 pages. We estimate with 95% confidence that the true population mean is
between 237 and 293 pages.
, Question 4
The population standard deviation for the heights of dogs, in inches, in a city is 3.7 inches. If
we want to be 95% confident that the sample mean is within 2 inches of the true population
mean, what is the
minimum sample size that can be taken? Round up to the nearest integer.
That is correct!
Answer: 14 dog heights
Question 5
Clarence wants to estimate the percentage of students who live more than three miles from
the school. He wants to create a 98% confidence interval which has an error bound of at
most 4%. How many students should be polled to create the confidence interval?
z0.10 z0.05 z0.02
5z0.01 z0.005
1.2 1.64 1.96 2.32 2.57
8
2 5 0 6 6
Use the table of values above.
That is correct!
Answer: 846 Students
Question 6
The average score of a random sample of 87 senior business majors at a university who took a
certain standardized test follows a normal distribution with a standard deviation of 28. Use Exce
to determine
a 90% confidence interval for the mean of the population. Round your answers to two decimal
places and use ascending order..
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