Question

1. Look in the newspapers, magazines, and other news sources for results of a survey or poll that show the confidence interval, usually shows as a +/- some amount. Describe the survey or poll and then describe the interval shown. How does knowing the interval, rather than just the main result, impact your view of the results?

2. How is the confidence level determined? Who in your workplace might set this level?

3. Should companies use the same confidence level each time that a confidence interval is determined, or should the level change based on situations? If it changes based on situations, what type of situations might call for higher confidence levels?

4. What do you think is a good confidence level and why?

5. Consider that your company just received a box of 500 widgets from a new supplier. You would like to know about how many of the widgets are defective. What would be your strategy to create a confidence interval for the proportion of defective widgets in the box? Include sampling strategy, number in sample, and statistical analysis.

6. Consider another student's strategy for this problem, and comment on the accuracy of this strategy. Also, consider increasing the number in the sample, and comment on how that might impact the results.

7. Assume that about 10% of the widgets were defective. Would the different sampling strategies described by other students result in different confidence intervals? Why, or why not?

Answer 1