Learning Materials
Features
Discover
Chapter 8: Q.11 (page 477)
If the Census did another survey, kept the error bound the same, and surveyed only people instead of , what would happen to the level of confidence? Why?
The confidence level decreases.
Over 30 million students worldwide already upgrade their learning with 91影视!
All the tools & learning materials you need for study success - in one app.
Get started for free
Announcements for 84 upcoming engineering conferences were randomly picked from a stack of IEEE Spectrum
magazines. The mean length of the conferences was 3.94 days, with a standard deviation of 1.28 days. Assume the
underlying population is normal.
a. In words, define the random variables X and
b. Which distribution should you use for this problem? Explain your choice.
c. Construct a 95% confidence interval for the population mean length of engineering conferences.
I. State the confidence interval.
ii. Sketch the graph.
iii. Calculate the error bound.
Suppose an internet marketing company wants to determine the current percentage of customers who click on ads on their smartphones. How many customers should the company survey in order to be % confident that the estimated proportion is within five percentage points of the true population proportion of customers who click on ads on their smartphones?
A telephone poll of adult Americans was reported in an issue of Time Magazine. Another question in the poll was 鈥淸How much are] you worried about the quality of education in our schools?鈥� Sixty-three percent responded 鈥渁 lot鈥�. We are interested in the population proportion of adult Americans who are worried a lot about the quality of education in our schools.
a. Define the random variables and in words.
b. Which distribution should you use for this problem? Explain your choice.
c. Construct a confidence interval for the population proportion of adult Americans who are worried a lot about the quality of education in our schools.
i. State the confidence interval.
ii. Sketch the graph.
iii. Calculate the error bound.
d. The sampling error given by Yankelevich Partners, Inc. (which conducted the poll) is . In one to three complete sentences, explain what the represents.
Table shows a different random sampling of cell phone models. Use this data to calculate a % confidence interval for the true mean SAR for cellphones certified for use in the United States. As previously, assume that the population standard deviation is 蟽= .
| Phone Model | SAR | Phone Model | SAR |
| Blackberry pearl | Nokia E71x | ||
| HTC Evo Design 4G | Nokia N | ||
| HTC Freestyle | Nokia N | ||
| LG Ally | Sagem Puma | ||
| LG Fathom | Samsung Fascinate | ||
| LG Optimus Vu | Samsung Infuse 4G | ||
| Motorola Cliq XT | Samsung Nexus S | ||
| Motorola Droid pro | Samsung Replenish | ||
| Motorola Droid Razr M | Sony W5a walkman | ||
| Nokia Twist | ZTE C |
If you decreased the allowable error bound, why would the minimum sample size increase (keeping the same level of
confidence)?
What do you think about this solution?
We value your feedback to improve our textbook solutions.
Explanations 
Textbooks 
Flashcards 
91影视 AI 
Notes 
Study Plans 
Study Sets 
Find a degree 
Magazine