Reference no: EM132848895
It is common to see many political polls in the months prior to an election. The polls attempt to estimate the percentage of voters that will vote for a candidate and how close the race is at that point. In close races, you will read headlines like the following:
1) Donald Trump is clinging to a two-point lead over Hillary Clinton in Georgia in the final days of the presidential election, according to a WSB-TV poll released on Friday.
2) The race for Georgia governor couldn't be closer just two months before the election, as an Atlanta Journal-Constitution/Channel 2 Action News poll showed Democrat Stacey Abrams and Republican Brian Kemp deadlocked at 45 percent.
In races that are not close, you read headlines that like the following:
1) The U.S. Senate race between Republican incumbent Johnny Isakson and Democratic political newcomer Jim Barksdale is not close, according to a new poll conducted by Survey USA for 11Alive.
2) Poll gives Nathan Deal a double-digit lead. A statewide poll conducted for 13WMAZ shows Republican Nathan Deal leading in the race for governor of Georgia.
To determine one headline or the other, two confidence intervals must be compared. Observe the article below.
Poll gives Nathan Deal a double-digit lead
A statewide poll conducted for 13WMAZ shows Republican Nathan Deal leading in the race for governor of Georgia.
In the poll, Deal had the support of 49 percent of likely voters, Democrat Roy Barnes had 38 percent and Libertarian candidate John
Monds had 9 percent.
Four percent of voters in the poll said they were undecided.
The poll's margin of sampling error is plus or minus 4 percentage points. The poll was taken Friday through Sunday and the results cover 599 registered voters in Georgia who said they were likely to vote in the fall election for governor. [www.ajc.com, September 13, 2010]
Notice that the margin of error is 4 percentage points. This means that from this poll of 599 registered voters, we estimate that the real percent of the millions of Georgia voters that will be anywhere from 49% plus or minus 4 percent, or 45% to 53% will vote for Nathan Deal. For Roy Barnes it would be 38% plus or minus 4%, or 34% to 42%.
Next, the two intervals from the population percentage are compared. Notice that they do not overlap. When this is the case, then you will read headlines that say, "one candidate has a large lead" or "this race is not close". If the intervals overlap, then that is when you will read that the race is "too close to call" or one candidate is "clinging" to a small lead over the other candidate.
One thing that is not included in the article above is the confidence level. It is most common to use 95%. We can calculate this same margin of error by first noting that 49% of 599 is 293 (rounded down). We can use the formula given in Section 6.3 to find the margin of error is E = 1.96(0.49)(0.51) 599
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(0.49)(0.51)599 = .040 or 4.0 percent. (see section 6.3 for more details).
Assignment: For this week's exercise, you are to search an internet search and find an article discussing survey results for an election. It can be for any election in any state as long as the article reports the number surveyed and the margin or error. Once you find the article, do the following:
a) Verify the margin of error by doing your own calculation. Include the calculation in your post. It is okay if the margin of error in the article is off by 0.1 from what you get (roundoff error).
b) Report the confidence intervals for the top two candidates in the article. Do they overlap or not?
c) Discuss the headline or the opening sentence of the article as it relates to your answer for part b.
d) Include at the end of your post a link to the article.