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0143ab93_videojs8_1563605_YT_2d24ba15 licensed under gpl3-or-later
Views : 1,145,451
Genre: Science & Technology
License: Standard YouTube License
Uploaded At Feb 19, 2023 ^^
warning: returnyoutubedislikes may not be accurate, this is just an estiment ehe :3
Rating : 4.174 (7,283/28,001 LTDR)
79.36% of the users lieked the video!!
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User score: 69.04- Positive
RYD date created : 2024-11-23T19:34:04.45517Z
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Top Comments of this video!! :3
The variable X is actually referring to two different values in the same expression. Variables, of course, are allowed to have multiple possible values, but the value they take on must be consistent throughout a calculation in order to be valid.
In the expression (1/2)(2x) + (1/2)(x/2), the first x is the smaller possible value, and the second x is the larger possible value. This is not a valid calculation because the variable x is misused.
An easy way to correct for this is to let x be the smaller value, so that the larger value is always 2x. We don't know whether our envelope has x or 2x in it, but we can calculate the expected gain/loss of switching.
If we have x, then switching gets us 2x, and 2x - x = x is the amount of change. If we have 2x, then switching gets us x, and x - 2x = -x is the amount of change. Both possibilities are equally likely, so the expected change is
E = (1/2)(x) + (1/2)(-x) = 0
Thus, there's no expected increase or decrease by switching.
1.5K |
Haven't watched part 2 but here's my guess: This calculation isn't accounting for the contents of the other envelope. When you switch you are not just gaining a new envelope, you are also giving up the one you picked. And these envelopes aren't independent; they are of course linked. We've defined the amount of money in the envelope you're holding as x but x is not actually constant here because it can have two different values. You're either holding the smaller amount, call it y, or the larger amount, 2y. So the true possibilities are: you're holding y, so switching gives you double (2y) and sticking gives you y; you're holding 2y, so switching gives you half (y) and sticking gives you 2y. Add these up and switching has a 50% chance of giving 2y and a 50% chance of giving y, while sticking gives a 50% chance of giving y and a 50% chance of giving 2y. Hence they are equal outcomes.
1.7K |
I feel this is for people that know the Monty Hall problem and now "know" that switching is always better...
The monetary amount is just a pointless distraction. There is a right, and a wrong envelope, or if you like, a winning and a losing envelope.
In the first choice, you have a 0.5 chance of picking the winning envelope. Te opportunity to switch gives you the exact same choice, with a 0.5 chance to pick up the winning envelope.
So no, it does not matter if you switch.
336 |
The real question isn't "should I switch?". The answer to that question is obvious. The real question is "Why is the simple math telling me I should switch wrong?" And that is much, much harder to answer and involves a deeper dive into relatively complex math for what seems to be a simple problem.
5 |
The sum of envelopes (S) is constant and not independent of choice. But in calculation for EV in first case S = 3x, in second S = (3/2)x which is changing interpretation for x. In the same manner we can ask how many is 5 apples plus 3 pears!
Ok, let's calculate EV using S which is constant.
Rewrite it in the context: EV = (1/2) 2x [where S = 3x] + (1/2)(x/2) [where S=3/2 x]
EV = (1/2) 2x [where x = 1/3 S] + (1/2)(x/2) [where x=2/3 S]
EV = x [where x = 1/3 S] + (x/4) [where x=2/3 S]
Let use S instead of x:
EV = 1/3 S + 2/3 (S/4) = 1/3 S + 1/6 S = 1/2 S
EV = 1/2 S - half of the sum of the envelopes. Simple.
4 |
The numbers in the equation are right but the original logic is wrong.
The variable (X) is not the same in both choices. If one envelope had $1 and the other had $2, then X would be either 1 or 2 depending on the first choice. So the equation would be
0.5*2($1) + 0.5*0.5($2) = $1.5
The average of the 2 choices, so switching or not doesn't matter [probability wise].
Psychologically, getting it wrong feels bad, but having it right then switching feels even worse.
38 |
@trucid2
1 year ago
Take two envelopes. Put $1 in one and $2 in the other. Pick one. Switch. Switch again. Keep switching. Each time you have 25% more money, on average. Gain infinite money. Retire.
8.3K |