Added "Somewhat Random Numbers"
This commit is contained in:
parent
b9751385d1
commit
bed4fd2766
81
src/Warm-Ups/Somewhat Random Numbers/main.typ
Normal file
81
src/Warm-Ups/Somewhat Random Numbers/main.typ
Normal file
@ -0,0 +1,81 @@
|
||||
#import "@local/handout:0.1.0": *
|
||||
|
||||
#show: doc => handout(
|
||||
doc,
|
||||
quarter: link(
|
||||
"https://betalupi.com/handouts",
|
||||
"betalupi.com/handouts",
|
||||
),
|
||||
|
||||
title: [Somewhat Random Numbers],
|
||||
by: "Mark",
|
||||
)
|
||||
|
||||
#problem()
|
||||
Alice generates 100 random numbers uniformly from $[0,1]$. \
|
||||
Bob generates 101 random numbers from $[0, 1]$, but deletes the lowest result.
|
||||
|
||||
#v(2mm)
|
||||
|
||||
Say we have both of the resulting arrays, but do not know who generated each one. \
|
||||
We would like to guess which of the two was generated by Bob. \
|
||||
What is the optimal strategy, and what is its probability of guessing correctly?
|
||||
|
||||
|
||||
#solution([
|
||||
Looking at the mean seems like a good idea, but there's a better way: \
|
||||
Assign the array with the smaller _minimum_ to Alice.
|
||||
|
||||
#v(3mm)
|
||||
|
||||
To compute the probability, generate 201 numbers. \
|
||||
Assign the first 100 to Alice and the rest to Bob. \
|
||||
Look at the lowest two numbers (of these 201, *before* Bob drops his lowest).
|
||||
|
||||
#v(8mm)
|
||||
|
||||
We'll use the following notation: \
|
||||
`AB` means the lowest was owned by Alice, and the second-lowest, by Bob.
|
||||
|
||||
#v(2mm)
|
||||
|
||||
Probabilities are as follows: \
|
||||
- `AA`: $100\/201 times 99\/200 approx 0.246$
|
||||
- `AB`: $100\/201 times 101\/200 approx 0.251$
|
||||
- `BA`: $101\/201 times 100\/200 approx 0.251$ // spell:disable-line
|
||||
- `BB`: $101\/201 times 100\/200 approx 0.251$
|
||||
|
||||
#v(4mm)
|
||||
Now, Bob drops his lowest number. \
|
||||
We'll cross out the number he drops and box the new lowest number (i.e, the one we observe):
|
||||
- #{
|
||||
(
|
||||
box(`A`, stroke: ored, inset: 1pt)
|
||||
+ box(`A`, inset: 1pt)
|
||||
+ box([: $approx 0.246$], inset: (top: 1pt, bottom: 1pt))
|
||||
)
|
||||
}
|
||||
- #{
|
||||
(
|
||||
box(`A`, stroke: ored, inset: 1pt)
|
||||
+ box(strike(`B`), inset: 1pt)
|
||||
+ box([: $approx 0.251$], inset: (top: 1pt, bottom: 1pt))
|
||||
)
|
||||
}
|
||||
- #{
|
||||
(
|
||||
box(strike(`B`), inset: 1pt)
|
||||
+ box(`A`, stroke: ored, inset: 1pt)
|
||||
+ box([: $approx 0.251$], inset: (top: 1pt, bottom: 1pt))
|
||||
)
|
||||
}
|
||||
- #{
|
||||
(
|
||||
box(`B`, stroke: ored, inset: 1pt)
|
||||
+ box(strike(`B`), inset: 1pt)
|
||||
+ box([: $approx 0.251$], inset: (top: 1pt, bottom: 1pt))
|
||||
)
|
||||
}
|
||||
#v(8mm)
|
||||
Alice has the smallest number in 3 of 4 cases, which have a total probability of $approx 0.749$.
|
||||
])
|
6
src/Warm-Ups/Somewhat Random Numbers/meta.toml
Normal file
6
src/Warm-Ups/Somewhat Random Numbers/meta.toml
Normal file
@ -0,0 +1,6 @@
|
||||
[metadata]
|
||||
title = "Somewhat Random Numbers"
|
||||
|
||||
[publish]
|
||||
handout = true
|
||||
solutions = true
|
Loading…
x
Reference in New Issue
Block a user