Originally Posted By: skaughtz
So I've been reading through all of the posts in the multiple threads on this topic and as someone new to this discussion here are my 2 cents on it, for what that's worth...
A lesson in quantitative statistical analysis would be well applied to this topic. To put it simply, nothing here validates a claim that Purolators tear more than any other filter. The sample size is absurdly low and ridiculously skewed. No one is cutting open and checking Mobil 1, Wix, K&N, etc., filters with either the same frequency or fervor as Purolator filters, and as such no statistically significant claim can be made that the latter tear more often. Only a gut feeling. Nor are any variables controlled in any way (unless OCIs, oil type, driving conditions, etc. are agreed to have no direct effect on filter condition). For all we know, issues such as those being observed could be an acceptable and predicted rate of occurrence for every 1 in 100, 1,000 or 10,000 filters of any brand. Does it appear to be a disturbing trend? Absolutely. Is it correct to say that a trend exists? Absolutely not. Further, 99.9% of Purolator buyers/users would likely never know even if an issue did exist, so it makes no sense to me for the company to publicly acknowledge the claims of a few people from a web forum (no offense intended... I was only clued in by an Amazon review mentioning that the topic existed on BITOG... as I was going to buy another PureOne for my next oil change).
What I do believe, however, is that this is a potential headache that I don't have the patience for and that ignorance is bliss. And who has time for all of that math? So I will be spending the extra $4 for Mobil 1 filters for my next oil changes until people start dissecting them and find issues that I am currently unaware of. Then I guess I'll just try to screw a sponge or a coffee filter or something onto my car instead.
Ok, lets talk experimental research statistics (really empirical research design). If you wanted to ask "does Purolator tear more than BrandX or x, y, and/or z, then yes, you would want to do a controlled experiment with the same conditions. That is because the brand itself would be the independent variable we want to deem significant. However, because this is not a "comparison between brands" but rather an issue of Purolator quality control/application. Is the Hudson more polluted that other rivers is a different question and design that asking if the Hudson River is polluted. You just test the item in question. Furthermore, the same "controlled" method might not return as rich of a dataset. "Fieldwork" is useful. You can't always do some work in controlled labs and return the same data as compared to the field. Think about running 70-100 sample test of all Purolator stock (including jobbers) on all vehicle makes from the last 25 years, on all motor oil weights and brands. Not really feasible. Worse if you do a dozen or so driving types, climates, commutes, etc. Thus when ask "are tears still and issue, small data-sets are still useful. You kinda answered the issue yourself.
Quote:
Further, 99.9% of Purolator buyers/users would likely never know even if an issue did exist
So if a few dozen that actually open the filter notice an issue (with some having back-to-back filter failures), there is a problem. From a stat standpoint, I might have an equal chance of winning the lottery than getting back-to-back filter failures. If it was 1 in 10,000, then bac k to back filters with different production dates should be 1 in 100,000,000. Getting multiple failure by such a small subset (BITOG), that 1 in 10,000 failure rate means that of the BITOG population, would have to had purchased and opened 610,000 Purolator filter to reach that mark in 6 or so months. If it was even 1 in 100, you should see 549 "everything is ok" filter threads for the 61 reported failure in the last year.
Now, lets take another example. Food poisoning from a restaurant as an example of a small sample. The question becomes, how do you know if there is an issue? Many people do not report food-poisoning to a local or state health health organization? Probably a similar number of folks who cut open filters depending the type of illness. If it is the mild-runs, maybe less. However, if you start seeing a cluster of reported issues from the same restaurant all with the same symptoms that is a big red-flag. So, out of the thousands and thousands of folks that might eat at a restaurant, you get a few dozen "hits"... that is significant. Especially if there was a lack of reported cases at the location for several years. So if you were on a website that tracked reported food-poisoning cases and it went from 1-2 cases in a year to 60 cases in 6 months, would you say there is a lack of evidence?
People cut open a lot of different filers and I would say those with Purolator are more likely to report it. Just like with food poisoning, once there are reports and a general awareness, other people who might not be likely to report will begin to report as well, swelling the data. If you started seeing WIX tears or Fram tears in a few cases, then you would likely see a increase in oil filter analysis. If Purolator did not have an issue, we might have only seen a blip of a couple of failed filters followed by a furry of "everything is ok" thread. Rather we say the opposite. A few initial reported filter failures followed by a lot of (former) Purolator users with the same failure.
