By using R studio 2.15 Textbook prices. The dataset is TextPrices and first you
ID: 664061 • Letter: B
Question
By using R studio
2.15 Textbook prices. The dataset is TextPrices and first you need to build a linear model with price as the response variable and number of pages in textbooks as the predictor.
a. Determine a 95% confidence interval for the mean price of a 450-page textbook in the population.
b. Determine a 95% confidence interval for the price of a particular 450-page textbook in the populatoin.
c. How do the midpoint of these two intervals compare? Explain why this makes sense.
d. How do the widths of these two intervals compare? Explain why this makes sense.
e. What value for number of pages would produce the narrowest possible prediction interval for its price? Explain.
Explanation / Answer
The CI (confidence interval) for the population mean (Mu) is the sample mean +/- confidence coefficient*standard error of the mean
The Confidence coefficient is the critical value for z of 95% confidence level = 95% of 450 = 427.5
The standard error of the mean = sigma/sqrt (n)
= 7/sqrt 40
So, the Confidence Interval is
25.5 +/- 1.96*7/sqrt 40
25.5 +/- 2.2
The lower bound is 25.5 - 2.2 = 23.3
The upper bound is 25.5 + 2.2 = 27.7
SO the Confidence Interval is (23.3, 27.7)
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.