×

Work out the standard deviation

A problem on brilliant was answered by 236 users in $$\frac{45}{24}$$ days, giving an average number of answers per day, $$\mu$$ $$(\approx 125.9)$$. Looking at this problem now, I see that three users answered it at times, $$\frac{15}{24*60},\frac{31}{24*60},\frac{69}{24*60}$$ days ago from now.

Taking into account the next person to post ( who could post at any time from right now to the end of $$7$$ days (very unlikely)) and the 4th last person to solve the problem (assuming, say, a constant probability of posting (although feel free to use a more realistic model)), estimate the standard deviation for the time intervals between people solving the problem.

For clarity: if the next person posts in $$\frac{t}{24*60}$$ days, and the 4th last posted $$\frac{T}{24*60}$$ ago, the differences are $$\frac{t+15}{24*60},\frac{16}{24*60},\frac{38}{24*60},\frac{T-69}{24*60}$$.

Note by A L
4 years, 9 months ago

MarkdownAppears as
*italics* or _italics_ italics
**bold** or __bold__ bold
- bulleted- list
• bulleted
• list
1. numbered2. list
1. numbered
2. list
Note: you must add a full line of space before and after lists for them to show up correctly
paragraph 1paragraph 2

paragraph 1

paragraph 2

[example link](https://brilliant.org)example link
> This is a quote
This is a quote
    # I indented these lines
# 4 spaces, and now they show
# up as a code block.

print "hello world"
# I indented these lines
# 4 spaces, and now they show
# up as a code block.

print "hello world"
MathAppears as
Remember to wrap math in $$...$$ or $...$ to ensure proper formatting.
2 \times 3 $$2 \times 3$$
2^{34} $$2^{34}$$
a_{i-1} $$a_{i-1}$$
\frac{2}{3} $$\frac{2}{3}$$
\sqrt{2} $$\sqrt{2}$$
\sum_{i=1}^3 $$\sum_{i=1}^3$$
\sin \theta $$\sin \theta$$
\boxed{123} $$\boxed{123}$$

Comments

Sort by:

Top Newest

How familiar are you with probability models? For example, if you assume that the events are independent and you can estimate the rate, then you can model it with the Poisson distribution.

A unique feature of the Poisson distribution, is that the mean is equal to the variance, which allows you to calculate the standard deviation.

Staff - 4 years, 9 months ago

Log in to reply

Hey Calvin, can you help me with another standard deviation problem please? I've even started the discussion but I have had no responses..

here is the discussion: https://brilliant.org/discussions/thread/calculation-of-standard-deviation-of-coordinates/

- 4 years, 6 months ago

Log in to reply

Which Brilliant problem was this? I would very much like to try it.

- 4 years, 9 months ago

Log in to reply

Either geometry/combinatorics or number theory (although only level 3- I'm new here!).

- 4 years, 9 months ago

Log in to reply

I think It's just a setting for the problem.

- 4 years, 9 months ago

Log in to reply

×

Problem Loading...

Note Loading...

Set Loading...