Discussion: Confidence Intervals

To prepare for this Discussion, consider the following scenario:

Polls will often present candidates running for election as winning or losing based on the results of recent surveys. When presenting the poll, there is usually information about a "margin of error." What does that mean?

For example, consider that one survey, conducted by a professional polling organization, shows Candidate Q leading the race by 49% with a plus or minus margin of error of 2 percentage points. The same survey shows the other candidate, Candidate Z, in second place with 47% of the survey results and the same margin for error.

However, consider that another survey taken of the same population in the same day by a different professional polling organization has different results. In this survey, Candidate Z leads the race with 49% while Candidate Q, has only polled 46%. This survey. This survey has a 3-percentage-point margin of error.

Review the textbook pages on the topic of confidence intervals for proportions. Consider the assumptions you would have to make to be able to compare the information given in these polls and explain the differences.  Then take your best guess as to who may be ahead in the race.

A 200- to 250-word explanation, listing the assumptions you would have to make to be able to use the information given in the polls and draw conclusions about a potential outcome.  Finally, based on what you know about confidence intervals, take your best guess about which candidate you believe is really ahead in the race. Justify your rationale and explain clearly how the assumptions you made affect your  prediction.

Read a selection of your colleagues' postings.

Respond by to two or more of your colleagues' postings in one or more of the following ways:

• Ask a probing question.
• Share an insight from having read your colleague's posting.
• Offer and support an opinion.
• Make a suggestion.
• Expand on your colleague's posting.

Return to this Discussion in a few days to read the responses to your initial posting. Note what you learned and the insights you gained from the comments your colleagues made.

Required Resources - Readings

Bluman, A. G. (2014). Elementary statistics: A step-by-step approach(9th ed.). New York, NY: McGraw-Hill. Chapter 7, "Confidence Intervals and Sample Size" (pp. 369-412).