Disc3
Discussion 3 ( 150 words and sources and References)
Understanding Polls—Confidence Interval
Many newspapers, when reporting results of political polls, say that “with 95% confidence, the results are in error by no more than +/- 3 percentage points.” The typical sample size is about 1,500. This allowance for error is intended to cover both sampling variability and the effect of small biases.
1. Assume that the poll (sample) indicates that just about 50% of likely voters favor a particular candidate. How large a +/- term is required for a 95% confidence interval for the population proportion?
2. Would the +/- term be much different if 40% of likely voters in the sample favored the candidate?
3. Why is the quoted +/- 0.03 larger than the +/- term you calculated in Question 1?
NOTE for this Discussion:
Discussion Outcome.
· Understand and be able to construct confidence intervals for the mean, and its interpretation and uses. Develop critical thinking regarding confidence intervals.
MORE ADVANCED STATISTICAL MEASURES
Required Reading
On parameters and statistics and populations and samples:
2. http://www.youtube.com/watch?v=SPnK-e1u01Y
On differences between sample and sampling distribution:
1. http://www.psychstat.missouristate.edu/introbook/sbk19.htm
On confidence intervals:
1. http://www.youtube.com/watch?v=R2vhjC5qCQk
2. http://onlinestatbook.com/lms/estimation/confidence.html
3. http://onlinestatbook.com/lms/estimation/mean.html
4. http://onlinestatbook.com/lms/estimation/confidenceM.html
5. http://onlinestatbook.com/lms/estimation/proportion_ci.html
6. http://onlinestatbook.com/lms/estimation/proportion_ciM.html
On Type I and Type II errors:
1. http://statistics.about.com/od/Inferential-Statistics/a/Type-I-And-Type-II-Errors.htm
Optional Reading
http://www.unc.edu/~nielsen/soci708/mod5/soci708mod5.pdf
http://www.itl.nist.gov/div898/handbook/prc/section1/prc14.htm