What grinds my gears…

[Swerd]

People fear what they don't understand. It's a truism that applies to many wonders of the modern age: microwaves, vaccines, cell phones, nuclear power, etc…

But microwave ovens aren't new. They've been around since the 1980s, or earlier. My kids grew up with them. It was only when they were in college did I hear the urban legend-type warnings about using them. I hadn't realized that the superstition about microwaves remains and has become a generational thing.

And, yes, most people figured out fairly quickly what plastic containers would melt or soften in them. Strangely enough, they're the same plastic containers that no one would dream of putting on a stove or in a standard oven.

 

[Steve81]

But microwave ovens aren't new.

Neither are nuclear reactors, but most people don't know what a positive void coefficient is and how that relates to Chernobyl versus modern reactor designs as an example.

 

[Swerd]

Neither are nuclear reactors, but most people don't know what a positive void coefficient is and how that relates to Chernobyl versus modern reactor designs as an example.

But many many homes have microwave ovens, and very few (if any) have nuclear reactors. So their vintage may be similar, but their familiarity is world's apart.

Reminds me of Back To The Future. Where's that Mr. Fusion we were all promised?

…most people don't know what a positive void coefficient is…

I know I'm one of those who don't. Quit showing off.

 

[Steve81]

But many many homes have microwave ovens, and very few (if any) have nuclear reactors. So their vintage may be similar, but their familiarity is world's apart.

Familiarity isn't understanding though. For many, a microwave is a magic box that heats up your food. If that's the extent of your knowledge on the subject, any scary rumor becomes plausible. Then when you google the evils of the microwave and find some whackjobs website talking about how they cause cancer, the rumors become absolute truth.

 

[rnatalli]

I tried Dollar Shave Club. The blades were good but I didn't like the angle on the head of the razor itself. Harry's works much better for me.

That's who I use. Their blades are good and work for me.


Sent from my iPhone using Tapatalk

 

[KEW]

Neither are nuclear reactors, but most people don't know what a positive void coefficient is and how that relates to Chernobyl versus modern reactor designs as an example.

Okay, damn it! I gotta know, what is a positive void coefficient and how does it relate to Chernobyl vs modern reactor designs (though the Chernobyl incident could not happen in Western reactor designs contemporary to Chernobyl)

 

[Steve81]

Okay, damn it! I gotta know, what is a positive void coefficient and how does it relate to Chernobyl vs modern reactor designs (though the Chernobyl incident could not happen in Western reactor designs contemporary to Chernobyl)

https://en.wikipedia.org/wiki/Void_coefficient

A positive void coefficient means that the reactivity increases as the void content inside the reactor increases due to increased boiling or loss of coolant; for example, if the coolant acts as a neutron absorber.

RBMK reactors, such as the reactors at Chernobyl, have a dangerously high positive void coefficient. This was necessary for the reactor to run on unenriched uranium and to require no heavy water. Before the Chernobyl accident these reactors had a positive void coefficient of 4.7 beta and after the accident that was lowered to 0.7 beta. This was done so all RBMK reactors could resume safe operation and produce much needed power for the then USSR and its satellites.

http://www.world-nuclear.org/info/Nuclear-Fuel-Cycle/Power-Reactors/Appendices/RBMK-Reactors/

In reactor designs where the moderator and coolant are of different materials, excess steam reduces the cooling of the reactor, but as the moderator remains intact the nuclear chain reaction continues. In some of these reactors, most notably the RBMK, the neutron absorbing properties of the cooling water are a significant factor in the operating characteristics. In such cases, the reduction in neutron absorbtion as a result of steam production, and the consequent presence of extra free neutrons, enhances the chain reaction. This leads to an increase in the reactivity of the system.

 

[herbu]

Now, I always go ask a real statistician.

One of my favorite non-intuitive examples is Let's Make A Deal.
3 doors w/ the grand prize behind one of them. You pick Door #1. The host reveals Door #3, and it does not have the grand prize. He then asks if you want to stick w/ your original Door #1 pick, or change your pick to Door #2. What do you do? Does it matter?

 

[Steve81]

One of my favorite non-intuitive examples is Let's Make A Deal.
3 doors w/ the grand prize behind one of them. You pick Door #1. The host reveals Door #3, and it does not have the grand prize. He then asks if you want to stick w/ your original Door #1 pick, or change your pick to Door #2. What do you do? Does it matter?

They actually covered that on Mythbusters (and in the movie 21 ).

 

[herbu]

They actually covered that on Mythbusters (and in the movie 21 ).

Cool. Didn't know that. Hope they got it right.

 

[Steve81]

Cool. Didn't know that. Hope they got it right.

They did. IIRC, they did a few hundred trials to test it out.

 

[Swerd]

One of my favorite non-intuitive examples is Let's Make A Deal.
3 doors w/ the grand prize behind one of them. You pick Door #1. The host reveals Door #3, and it does not have the grand prize. He then asks if you want to stick w/ your original Door #1 pick, or change your pick to Door #2. What do you do? Does it matter?

I'd stay with Door #1. With Door #3 eliminated you have a 50/50 chance of winning the prize. No different if you pick Door 2.

Am I missing something simple here?

 

[Steve81]

I'd stay with Door #1. With Door #3 eliminated you have a 50/50 chance of winning the prize. No different if you pick Door 2.

Am I missing something simple here?

https://en.wikipedia.org/wiki/Monty_Hall_problem

 

[Swerd]

https://en.wikipedia.org/wiki/Monty_Hall_problem

Thanks for the link. This is another example why I don't trust my intuition when it comes to statistics .

 

[Steve81]

Thanks for the link. This is another example why I don't trust my intuition when it comes to statistics .

It sounds like it should be total hogwash on the face of it, but this part of the wiki makes it a little more understandable:

Vos Savant suggests that the solution will be more intuitive with 1,000,000 doors rather than 3. (vos Savant 1990a) In this case there are 999,999 doors with goats behind them and one door with a prize. After the player picks a door the host opens all but 1 of the remaining doors. On average, in 999,999 times out of 1,000,000, the remaining door will contain the prize. Intuitively, the player should ask how likely is it, that given a million doors, he or she managed to pick the right one initially.

 

[herbu]

I'd stay with Door #1. With Door #3 eliminated you have a 50/50 chance of winning the prize. No different if you pick Door 2.

And that's why this is one of my favorite non-intuitive examples.

It is also how statistics can be used to befuddle even the smartest people, if they don't have a statistical background. When you do this to somebody once, they hesitate to question your "statistical conclusion" in the future. Many a business decision was based on erroneous but unchallenged statistics. I know.

 

[slipperybidness]

Oh yes, this is a very tricky one, classic example of stats

 

[herbu]

https://en.wikipedia.org/wiki/Monty_Hall_problem

One part of this wikipedia article is questionable.

"Vos Savant's response was that the contestant should switch to the other door (vos Savant 1990a). Under the standard assumptions, contestants who switch have a 2/3 chance of winning the car, while contestants who stick to their choice have only a 1/3 chance."

It should say contestants who switch have a 1/2 chance.

If you pick one out of three doors, your chance is 1/3. It doesn't matter what happens next. If you keep your pick, your chance started at 1/3 and stays 1/3.

But if you pick one out of two doors, your chance is 1/2. Again, regardless of who opens what, your chance of winning remains 1/2.

 

[Steve81]

One part of this wikipedia article is questionable.

"Vos Savant's response was that the contestant should switch to the other door (vos Savant 1990a). Under the standard assumptions, contestants who switch have a 2/3 chance of winning the car, while contestants who stick to their choice have only a 1/3 chance."

It should say contestants who switch have a 1/2 chance.]

Negative. If you look at the simple solution section, it shows the breakdown of the possibilities.

Also from that section:

As Cecil Adams puts it (Adams 1990), "Monty is saying in effect: you can keep your one door or you can have the other two doors". The 2/3 chance of finding the car has not been changed by the opening of one of these doors because Monty, knowing the location of the car, is certain to reveal a goat. So the player's choice after the host opens a door is no different than if the host offered the player the option to switch from their original chosen door to the set of both remaining doors. The switch in this case clearly gives the player a 2/3 probability of choosing the car.

Of course for a simpler explanation:

If you pick one out of three doors, your chance is 1/3. It doesn't matter what happens next. If you keep your pick, your chance started at 1/3 and stays 1/3.

Since the car must be behind one of the two remaining doors, and you're accepting that there is a 1/3 chance that its behind the door you originally chose, then there must be a 2/3 chance that its behind the door you didn't.

 

[herbu]

Negative. If you look at the simple solution section, it shows the breakdown of the possibilities.

Also from that section:


Of course for a simpler explanation:



Since the car must be behind one of the two remaining doors, and you're accepting that there is a 1/3 chance that its behind the door you originally chose, then there must be a 2/3 chance that its behind the door you didn't.

Hahahaha! You're taking me back to the debate we had in class. (One that, by the way, I lost.)

My position was if the guy changes his door, the first game essentially ends and a new game begins w/ a 50/50 chance. The right answer, (yours), is that the initial game does not end... it continues.

The fact that there are 2 answers, both of which can be explained in an apparently sensible manner, is further evidence that statistics can be a slippery slope.