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seen Sep 13 at 13:26

Jul
2
awarded  Curious
Jun
11
awarded  Yearling
Mar
29
awarded  Nice Question
Mar
26
comment Normal distribution percentile calculation
Intuitive answer: 97.8% (less than 99%) of the parcels will be less than 2 deviations above the mean. 2 deviations above the mean is 19 pounds, so 16.465 can't possibly be right (even excluding the extra pound). Incidentally, this model isn't very good because it states that some packages will weigh less than 0 pounds.
Mar
26
comment love in an elevator
Possibly simpler: combined weight of 16 people averages 1200kg with a standard deviation of 40kg (variance increases linearly with the number of people, so standard deviation increases with the square root of the number of people). As noted above, the chance this exceeds 1140kg is the chance the standard normal variable exceeds -1.5 standard deviations, or about 0.9332 as noted above
Mar
26
comment love in an elevator
@JoelReyesNoche What's love but a second-hand emotion?
Mar
26
comment What is the cartesian equation of $r = 1 + r \sin(\theta)?$
Well, r^2 = x^2 + y^2 and tan(theta) = y/x, and go from there.
Mar
13
accepted Population average age decreases with births AND deaths (kind of)?
Mar
13
comment Population average age decreases with births AND deaths (kind of)?
Of course! As long as the age decrease I describe is slower than the flow of time, the average age still increases. I will approve this answer as soon as stack lets me.
Mar
13
asked Population average age decreases with births AND deaths (kind of)?
Feb
28
answered Deriving the Area of a Sector of an Ellipse
Feb
27
answered How to calculate ellipse sector area *from a focus*
Feb
23
comment Calculating a Point that lies on an Ellipse given an Angle
@Atraxia this may help: math.stackexchange.com/questions/493104/…
Feb
23
comment Ellipse in polar coordinates
You may also want to look at my answer to math.stackexchange.com/questions/493104/…
Feb
23
answered Evaluating $\int_a^b \frac12 r^2\ \mathrm d\theta$ to find the area of an ellipse
Feb
20
comment Explain $\iint \mathrm dx\mathrm dy = \iint r \mathrm d\alpha\mathrm dr$
Why not take the area of the entire triangle (r^2/2*dtheta) and integrate over theta? ;)
Feb
5
awarded  Popular Question
Feb
1
revised Why is this coin-flipping probability problem unsolved?
fixed probability
Feb
1
answered Why is this coin-flipping probability problem unsolved?
Feb
1
comment Why is this coin-flipping probability problem unsolved?
What if you know in advance the coin will come up heads p% of the time, even for p!=50? That's sort of the question I asked at: quant.stackexchange.com/questions/2172/… (and no answers there yet either)