The Reduction Funnel and the Rule of Thirds

[dmaziuk]

After much accurate criticism over many years for a lack of appropriate emphasis on gas planning in the OW course, PADI added a decent gas planning section to their OW course. I was one of the people who leveled that criticism, especially in a discussion with PADI headquarters while I was getting a Distinctive Specialty on dive planning approved.

...

I am afraid of what is going to happen. Wanting to be sure students get the question right on the exam, instructors will emphasize the rule of thirds. As a result, we will reach the point that all recreational diving is supposed to follow the rule of thirds, just as the school district in which I worked decided that all essays had to follow the only model they saw in their training. I am beginning to sense that it is inevitable.

And now you know why they say what they say about good intentions.

 

[Bob DBF]

You are right, of course. What is worse is that many will read your long essay and distill it down to what they think is the essence: "PADI sucks," and cite your post as proof.

that would be ironic considering he is PADI's biggest defender when the rest of us say anything negative about them

Ironic and overlooks the insight on the operation of any large company or bureaucracy. This is great example of how "training by catchphrases" evolves from education. It is not an issue that just applies one scuba agency, or institution.

The issue at hand will be, are the instructors going to teach gas planning or just teach the test. It's the instructor don't you know.


Bob

 

[boulderjohn]

Here is another example of how it happens in scuba.

For years the PADI OW course had a section on identifying a panicked diver. They had a list of all the things to look for that might indicate a diver is in panic. One of them is equipment rejection. Equipment rejection often includes discarding the regulator. It can also involve shoving off the mask. If the mask is shoved off by a panicked diver, it could end up askew on the forehead.

The question on the exam asked students to identify a sign of panic in a diver. the correct answer in the multiple choices was a mask on the forehead.

I assume that instructors reviewing for the final exam and wanting to make sure that students got that question right is where we got the idea that placing your mask on your forehead will result in a DM leaping at you in full rescue mode. The original full concept got reduced to one simple and inaccurate idea.

 

[northernone]

That is just about a textbook example for when you should use the rule of halves (usable gas = starting pressure - min gas; use half usable on way out, half on way back, finish with your min gas). Of course it's fine to turn earlier but it isn't required, and you could surface at any time and swim back.

That is just about a textbook example for when you should use the rule of halves (usable gas = starting pressure - min gas; use half usable on way out, half on way back, finish with your min gas). Of course it's fine to turn earlier but it isn't required, and you could surface at any time and swim back.

True. OW water dive, we don't 'need' to make it back to shore on the bottom.

I generally do just because it's convenient. Not a safety issue. (debatable I suppose with boat traffic, currents and weather conditions I suppose but generally not a safety issue) I don't do halves for my context though because I like a little extra air for dealing with entanglements and I dislike surface swims.

Half sounds fine.... Because you can just surface anywhere and aren't required getting back subsurface. The boat down line example sounds like a similar situation.

Just caught myself reasoning in favour of 1/3rds. Oops. I generally think they do not belong in OW diving. Safety stop at 500psi (cylinder dependant of course) or so seems to work great for recreational profiles.

I dislike the guides who suggest surfacing with a 1000psi. Seems disingenuous in benign conditions as simply a way to get rid of their customers faster.

Regards,
Cameron

 

[dorsal]

Years ago, while I was teaching educational processes, I came up with a concept I called the Reduction Funnel, which I believe works in almost all avenues of life. The basic idea is that someone or some group does a lot of thinking and research leading to a concept that they expect will provide a serious benefit in their line of work. It is necessarily complex, and they have thought out all the different possibilities and contingencies. They publish the concept, producing well-designed explanations.

John. What you clearly described happens far too often. Business is full of this example. How many business books are out there like who moved my cheese.

I’m going to borrow the Reduction Funnel phrase.

 

[boulderjohn]

I’m going to borrow the Reduction Funnel phrase

Be my guest.

 

[Kevrumbo]

Years ago, while I was teaching educational processes, I came up with a concept I called the Reduction Funnel, which I believe works in almost all avenues of life. The basic idea is that someone or some group does a lot of thinking and research leading to a concept that they expect will provide a serious benefit in their line of work. It is necessarily complex, and they have thought out all the different possibilities and contingencies. They publish the concept, producing well-designed explanations.

Soon some key people in an organization leadership buy into the system and formally adopt it. They send a group off for training, and those people take a thorough course and get thorough training materials. They return to the organization with the task of training the next level of trainers. Knowing people will not have time for the training they had, they shorten the training time considerably, and they produce new, condensed training materials. The people they train that way then go out and train others in even shorter sessions with even more condensed training materials. Before you know it, the original complex, well thought out program has been reduced to a few shoutable slogans and examples that in no way represent the original and which may even prohibit the perfectly acceptable options that were present in the original design but were not included in the condensed training materials.

I first thought about this when I joined a school district as a English teacher and had to teach their system for essay writing, a highly rigid, formulaic system that had almost nothing to do with good writing as I had learned it. All essays through 12th grade had to be written according to this formula, even when that system was totally wrong for the topic. I asked everyone why, and I was told that was the way it had to be done. I was referred to the original program, contained in large, dust covered volumes that had clearly not been opened in years. I read through it, and saw the problem. The original system was not rigid. It was not formulaic. It had some principles that made sense, and it had a lot of options for choosing the right approach for the right topic.

But in that first section, it made a key strategical error. It showed ONE example of how this approach could be used in ONE kind of writing. I recognized the example: it was the ONE that was used as a model for ALL the writing that was to be done in the school district. The idea that there were other acceptable ways to do it was entirely lost in the reduction funnel of teacher training. More importantly, the original program emphasized that the example was for a very basic writing topic, one suitable for middle school, but not for more complex writing. (The school district required it through 12th grade.)

So what has this got to do with the rule of thirds in diving?

After much accurate criticism over many years for a lack of appropriate emphasis on gas planning in the OW course, PADI added a decent gas planning section to their OW course. I was one of the people who leveled that criticism, especially in a discussion with PADI headquarters while I was getting a Distinctive Specialty on dive planning approved. My course included planning options such as all usable, the rule of halves, and the rule of thirds and talked about when each would be appropriate. In those discussions, the representative from PADI headquarters who eventually approved my course mentioned that while all of those were valid gas planning strategies, the rule of thirds would not be used all that often in recreational diving.

When PADI added gas planning to the OW course, they put a question about it on the final exam. For some reason, they used the rule of thirds as the planning strategy that the divers were using in the question. There is nothing wrong with the question, and the way the students are supposed to calculate the turning point for the dive is correct if you are using the rule of thirds. Unfortunately, it is the only question of that type on the exam.

I am afraid of what is going to happen. Wanting to be sure students get the question right on the exam, instructors will emphasize the rule of thirds. As a result, we will reach the point that all recreational diving is supposed to follow the rule of thirds, just as the school district in which I worked decided that all essays had to follow the only model they saw in their training. I am beginning to sense that it is inevitable.

In the last couple months, I have seen several comments in ScubaBoard that indicated that the rule of thirds is something that must be followed on all dives, and I fear that it won't be long before that becomes a hard and fast law that cannot be violated. People who talk about other ways to plan a dive will be ridiculed for being unsafe.

A way of thinking about the rule of thirds is that you MUST get back to your ascent point, which in a cave is usually your exit point. On an open water dive, it could be descending on a mooring line to a wreck, with the knowledge that you really want to get back to that line for your ascent.

Here is another example of how it happens in scuba.

For years the PADI OW course had a section on identifying a panicked diver. They had a list of all the things to look for that might indicate a diver is in panic. One of them is equipment rejection. Equipment rejection often includes discarding the regulator. It can also involve shoving off the mask. If the mask is shoved off by a panicked diver, it could end up askew on the forehead.

The question on the exam asked students to identify a sign of panic in a diver. the correct answer in the multiple choices was a mask on the forehead.

I assume that instructors reviewing for the final exam and wanting to make sure that students got that question right is where we got the idea that placing your mask on your forehead will result in a DM leaping at you in full rescue mode. The original full concept got reduced to one simple and inaccurate idea.

John, these are all examples describing the differences between Inductive and Deductive Reasoning, in which your "Reduction Funnel" schema can illustrate the logic flow bidirectionally, either from bottom-to-top or top-to-bottom.

Inductive reasoning, also known as ‘bottom-up’ logic is the kind of reasoning that focuses on creating generalized statements from specific examples. This type of reasoning focuses on specific examples that may prove something true, which are then transferred onto generalized concepts.

Deductive reasoning differs from inductive because deductive tries to use generalized concepts to try and pinpoint specific information. This is also known as ‘top-down’ approach or a waterfall approach. This is because the researcher starts with a generalized concept and then works his way to a specific example.

 

[Kharon]

If you say it forcefully enough from a respected platform,
If you repeat it enough,
It will become gospel.

Now...What credence shall we then grant this gospel?

Why my guiding idiom is "I believe in disbelief."

True. OW water dive, we don't 'need' to make it back to shore on the bottom.

Depends on where you "shore" dive. When my club was on GC I found that the "shore" was a wall of old devils tooth coral. Though flat on top, it was impossible to walk across even if you could climb up onto it. So this "shore" diving was essentially a single point entry/exit. You couldn't just surface anywhere and exit. It required either very good nav skill or a surface swim.

I really don't consider this true shore diving (just me, I know). Shore diving to me is a dive that allows you to exit the water anywhere along the water/land interface - most (though not all) dives on Bonaire for example.

I needed to be careful to hold more air in reserve on GC just in case than I ever do on Bonaire. Not thirds, not halves, just an indefinable more based on the circumstances during the dive - kinda' like - "eh, think it's time I better head back".

 

[dmaziuk]

Deductive reasoning differs from inductive because deductive tries to use generalized concepts to try and pinpoint specific information. This is also known as ‘top-down’ approach or a waterfall approach.

Often accompanied by "the kitchen sink syndrome" because the result is "necessarily complex, and they have thought out all the different possibilities and contingencies". Whereas in reality the "different possibilities and contingencies" don't happen 99% of the time, and nobody can figure them out. They can only memorize the "right" answers.

 

[Bob DBF]

Shore diving to me is a dive that allows you to exit the water anywhere along the water/land interface

You must live a sheltered life, the majority of my shore dives involve having to exit where you enter. Although you might find a place to get out of the water, you probably be trapped there or have to ditch your gear to make it off the beach. Where I dive in NorCal, there are bluffs and cliffs along the ocean and most of the lakes in the area. A year or three ago, four were rescued and one or two died when they got out of the water in the wrong spot by Ft Bragg, Ca.

For that reason, and I don't want to carry my gear more than necessary to get back to the truck, I plan on coming out of the water where I came in.

YMMV


Bob