I was reading some threads in one of the famous Filipino Forums (Pinoyexchange.com) otherwise known as PEX for short, and I found this article posted (see complete article below).   I don’t know exactly who originally wrote this but it made sense to me.. at first that is (let me explain)

I’m not a mathematician or a statistics major but certainly I can do some calculations using my spreadsheet.

It seems like the author is right in saying that  if you backtrack the formula,  using the 2100 respondents value, you can come up with  the population assumed which is  13,125 (for the SWS survey) and for the pulse asia survey, at 1800 respondents, working on the formula would give 6,429 as the population.

So let me try out the formula and plugin an assumed population of 50,000 voters.  I get a value of 2380.95  which is not at all far from the  2100 value used by SWS.

n = N / (1 + Ne^2)

where n = sample size
N = population size
e = margin of error

Then I tried out 50,000,000 and plug it into my spreadsheet and see how much ’sample size’ will a population of 50,000,000 would need.  I was hoping to see  something like a few hundred thousand but when I  saw the result,  using the formula, it says that I only need a sample size of  2499.88  HUH???

50,000 population needs 2381 sample size and  50 million needs 2500 sample size?  That’s a difference of only (2500 – 2381 = 119).

Meaning to say,  if you have 50,000 voters, with the Slovin’s formula you can accurately predict by talking to just 2381 people  and if you ask  a couple more people (119 more) you can say that you can actually predict for a population of 50,000,000 voters?  That doesn’t sound right.

Does this mean that  theorically if  SWS  or Pulse asia  conducted a survey with 2,500 respondents then statisticians can say that it is a good and valid sample size?

Check it out.  Here’s a screen cap of the spreadsheet

See the screen cap above.    You can see that the difference between the population size results in very little changes in the sample size.  I don’t know about you but for me,  I really don’t think that such a small sample size can accurately predict the outcome of the 2010 elections.

But then again, I totally agree with the writer’s point at the end which is

Before you believe that SWS and/or Pulse Asia survey results are what can actually be expected if elections were held then and there, think more than twice; it is also highly likely that the results may not really be reflective of what the entire Filipino electorate may actually and ultimately reflect, from a statistical standpoint.

Here’s the complete acticle I was talking about

http://www.pinoyexchange.com/forums/showthread.php?p=42735928

A Take on SWS and Pulse Asia Surveys

Not only have I been studying and teaching statistics as a college instructor, but I have also been using it as a scientist and researcher for quite some time now. However, it was only during the early morning of March 26, 2010 that I thought of trying to scrutinize SWS and Pulse Asia surveys from a statistical standpoint. Although SWS and Pulse Asia never reveal how they actually conduct the surveys (aside from indicating the questions asked, the number of respondents, and the margin of error they set) and that they usually argue that their methods are “tried and tested” ones, I think it would not hurt if we try to take a look at how representative their survey results are of the entire population of registered voters, using another generally accepted and “tried and tested” method we use in statistics.

I’m talking about Slovin’s formula.

It is only from members of a sample (as respondents) that data would be obtained through a survey, since a census (or gathering data from the entire population) is not feasible for data gathering given a short span of time and limited resources. It is important, however, that the sample used be as representative of the population as possible, so that inferences derived from analysis of sample data may be more or less applicable to the whole population. This may be ensured by using appropriate sampling methods and using appropriate sample sizes.

In statistics, Slovin’s formula is a generally accepted way of how to determine the size appropriate for a sample to ensure better representation of the population of a known size. The formula may be expressed as follows:

n = N / (1 + Ne^2)

where n = sample size
N = population size
e = margin of error

Again, in the context of SWS and Pulse Asia surveys, these groups could argue that they use formulas other than Slovin’s formula in coming up with sample sizes of 2,100 and 1,800 respondents respectively (I did a review of news clips from the ABS-CBN News web site, and noted that these two figures are the most commonly used sample sizes of the two survey groups). However, if we use Slovin’s formula (which is, again, a generally accepted and commonly used method in statistics), rather alarming ideas may be derived (alarming, considering how some Filipinos base and defend their decisions on who to vote for on survey results).

Considering that both survey groups usually set the margin of error at plus or minus 2 percent (or 0.02), here’re what Slovin’s formula says about the SWS and Pulse Asia sample sizes (anybody with a considerable aptitude in algebra may verify these):

* SWS’s survey over 2,100 respondents, with margin of error set at 0.02, assumes a population composed of only 13,125 individuals. In the context of election-related surveys, that would point to the survey results being possibly representative of a population of 13,125 registered voters nationwide.

* Pulse Asia’s survey over 1,800 respondents, with margin of error set at 0.02, assumes a population composed of only 6,429 individuals.In the context of election-related surveys, that would indicate that the survey results may be representative of a population of 6,429 registered voters nationwide.

Now let’s see…. Based on Slovin’s formula, the SWS sample size seems to assume that there are only 13,125 registered voters, while the Pulse Asia sample size seems to assume that there are only 6,429 registered voters nationwide. How many registered voters are there in the country? Can anyone provide the actual population size of registered voters? Is there anybody reading this who knows anyone from COMELEC? I’m sure there’s a definite figure.

Well, with or without the actual figures from COMELEC, I believe 13,125 and 6,429 are gross underestimations of the actual number of registered voters in the country.

I’m not trying to disprove SWS or Pulse Asia here. Again, it is highly likely that they are using methods that do not include Slovin’s formula. However, here’s my case in point: Before you believe that SWS and/or Pulse Asia survey results are what can actually be expected if elections were held then and there, think more than twice; it is also highly likely that the results may not really be reflective of what the entire Filipino electorate may actually and ultimately reflect, from a statistical standpoint.

And that is not yet considering the sampling method employed by these survey groups.

Hence, to the SWS and Pulse Asia survey frontrunners and their supporters, I suggest for you not to keep your hopes too high, or you may end up disappointing yourselves if the actual results of the elections will not reflect the trends reflected by those survey results. And to survey tailenders and their supporters, there may actually be valid bases for you not to give much credence to these survey results. Quoting from Sen. Gordon: “The real ’survey’ is on May 10, 2010.”

I was reading a recent article from Businessmirror and this part got my attention

These sectors are coming around to the view that our local pollsters are doing a great disservice to the public and to the social-science profession by using flawed, even long-discarded, methods in their determination of public opinion, and then issuing the polling results in a skewed, helter-skelter way, without as much as offering the obligatory caveats about their work. They are also being taken to task for their adroit (some suggest deceptive) “marketing” operations as they actively promote their “studies” and seek “sponsors” (subscribers is how these firms call them) to cover the costs of their operations.

Hmm…some really strong point there.   I guess these are the times when a few people would like to be associated with these survey companies.  Anyway, going back to the article,  it also stated that Sen Kit Tatad was a victim of a flawed survey result.

… has actively sought greater transparency and accountability on the part of SWS and Pulse Asia. In our regular Kapihan sa Sulô forum last Saturday, Tatad asked that these firms refrain from surveying and purveying the results in the meantime until they can clear themselves, as it were, from past mistakes and indiscretions. Said Tatad: “SWS should first explain its fatally flawed exit poll of the 2004 elections in Metro Manila before it conducts yet another opinion poll related to the May 10 elections”.

The story goes on with mentioning of a specific example regarding the results of the last election between Arroyo and Fernando Poe. Survey says that Arroyo got 31% while FPJ got 23% of votes in Metro Manila. After the official Comelec figures came out, it was FPJ who won in Metro Manila with 36% while Arroyo got 26.46%.

I also learned form that article that there’ is this book called “The Opinion Makers” where Moore concluded that pollsters “do not measure public opinion, they manufacture it.” He anchors this contention on the practice of polling firms to gloss over “voter indecision” during an election campaign.

Here’s the cover of the book “The Opinion Makers”

Here’s what Publisher Weekly said about it…

Moore argues that today’s polls report the whims rather than the will of the people due to an intrinsic methodological problem: poll results don’t differentiate between those who express deeply held views and those who have hardly, if at all, thought about an issue. Thus, respondents are compelled to provide an ill-considered, top-of-mind response because the method does not offer the option of expressing no opinion. In Moore’s view, forced-choice polls not only distort public opinion, they create a legitimacy spin cycle, which damages U.S. democracy by manufacturing a public consensus to serve those in power.

So I guess this does not only happens in the Philippines but in all sorts of political polls. The sad part is that, I think this is happening again in this 2010 elections.

I just hope people will not be swayed by these surveys and still vote whatever they feel is the right candidate for them.

Election time again and political candidates are doing whatever they can to ‘look good’ on surveys. I’ve always wondered how accurate are these SWS surveys and can they really measure the ‘pulse’ of the people?

I read an article in Inquirer. One specific SWS survey covered 2,100 registered voters. So the question is, can a pool of 2,100 survey respondents provide a really good measure? I don’t know but in my humble opinion, I don’t think so. I think we need to have much more respondents than that and probably factor in some of the areas where certain candidates are known to do well on certain provinces, or those who can get “mass votes” like the ones from Iglesia ni Cristo or other groups of people who vote solidly.

The “benefits” of surveys

I think one of the “benefits” of surveys for candidates, (if you can even call it a benefit) is that it can “convince” people who are rooting for candidates at the bottom of the survey to “jump ship” and vote for a candidate who ranks pretty well. I guess there are some people who will “vote” for a candidate with a better chance of winning than vote for a losing candidate. Undecided voters can also be enticed to vote for the “popular”. Such “swing votes” are a huge part of the political game and can greatly affect the outcome of an election.

The “Thinking Filipino”

This 2010, I believe is the year of the “Thinking Filipino”. With traditional media/internet/ and other sources, more and more Filipino voters are becoming aware of what’s happening in our country. Even students are better informed about the candidates, their achievements, and their political platforms. I say vote for the candidate that your heart and conscience tells you to vote, regardless of what any survey says.

Here are some of the people’s actual reactions and thoughts about these surveys. These are taken from facebook.

Chiz Escudero Biography

Francis Joseph Guevara Escudero, popularly known as Chiz Escuderro was born on Oct 10, 1969. His father is the former Agriculture Secretary Salvador “Sonny” H. Escudero III and educator Evelina B. Guevara.

Chiz Escudero Education

Chiz Escudero attended the University of the Philippines Integrated School (UPIS) from elementary until high school. He graduated 1981 and 1985 respectively.

He attended college in UP diliman with a Bachelor’s Degree in Political Science, and proceed to take up law at the same university and graduated 1993. He received his Masters in International and Comparative Law at the Georgetown University Law Center in Washington D. C. in 1996.

Chiz Escudero Political Career

Chiz started his political career at age 28 back in 1998 when he became the representative of the 1st District Sorsogon for the 11th Congress.

Escudero aimed at a Senate seat and on Jan 30, 2007 he filed for his candidacy for Senator. He got the 2nd highest tally of votes. Sen Loren Legarda got the highest. His achievement included having files 224 bills and resolutions of significance.