Understanding Political Polls

The two tables above summarize three recent polls conducted in South Carolina. (CLICK ON THE TABLE TO MAKE IT LARGER)

The top table shows a "point estimate" of the percentage of South Carolina voters planning to vote for each candidate. Is this the true percentage? Maybe but probably not. The truth may be less than or greater than the point estimate.

To get a better estimate of the true percentage, the poll includes a margin of error. By applying the margin of error to the point estimate, we strengthen the estimate by adding a lower and upper bound to the truth. The second table applies each poll's margin of error to each candidate's point estimate. For example, in the Clemson poll, the estimated percentage of voters planning to cast a ballot for John McCain was 29%. Applying the margin of error (4.6%), we can now say the estimated percentage of voters planning to cast a ballot for John McCain is at least 24.4% and at most 33.6%.

Don't just compare the point estimates of two candidates. Instead, compare the upper and lower bounds. If the ranges (of two candidates) do not overlap, there is statistically significant separation between the two candidates.

The margin of error is based on two main factors: Sample size and confidence level. Obviously, the larger the sample size, the better the estimate. A larger sample size will decrease the margin of error. The confidence level is a measure of strength for the estimate. Most results of political polls are stated with 95% confidence. This means there is a 95% probability that the upper and lower boundaries contain the true percentage. There is a 5% probability that the true percentage lies outside the range.

I hope this helps.

Unspoken Needs

This is an article that recently appeared in the Daniel Island News.

If you had told me twenty years ago that I would someday use probability to convey a New Year's message, I would have choked on my excessive laughter. But, here it is-

I googled “top ten new years resolutions” and the first returned site listed the following: Spend more time with family and friends, fit in fitness, tame the bulge, quit smoking, enjoy life more, quit drinking, get out of debt, learn something new, help others, and get organized.

The commitment that caught my eye was “help others”. As described on the site, this entails volunteering our time. Opportunities are usually obvious in a community with ample avenues for volunteerism-churches and civic organizations come to mind.
But what about the unspoken needs in a community? These are people that, on the surface, seem fine but internally struggle with physical, emotional, or financial issues. It is their personal battle but they cannot and should not fight alone.

So, how about this for a resolution: Seek ways to address the unspoken needs of our community.
There are a myriad of unspoken needs. I made a list of five issues that, in my opinion, people quietly deal with in America. The list included emotional, physical, and financial pressures. I was able to find prevalence rates (percentage) for each one expressed as number of cases per 100,000 people. Of the ones I researched, the lowest rate was 0.01%. So, I used this as an estimate for an unspoken need rate.

I applied the rate to the population of Daniel Island, which was 5500 as of spring 2007. (as reported on http://www.danielisland.com/) At an estimated rate of 0.01%, the probability of at least one person on Daniel Island having an unspoken need is approximately 42.3%. Table one shows approximate probabilities for various numbers of people.

Now, I don’t know how to address these needs. I just know they exist and the people walk by us every day in the grocery store, at school, at the ball game, at church, and in the restaurant. Our resolution should be to gain wisdom and vision to notice the less than obvious needs. We should resolve to consistently think of people with unspoken needs and, on their behalf, ask that a message of hope be brought to their heavy hearts and clouded minds. A message that, once received, will give them a new perspective for living and will slowly and surely remove the burden carried for too long.

Happy New Year to all!