What is a Langevin Rate?
470847
"Over the last century, many scientists have discussed the collisional rate of an ion with a polarizable neutral. Langevin began the discussion in 1905 with work outlining the attractive potential between a point charge and a point-polarizable neutral. The result was an expression for the collisional rate constant, k, in terms of a few simple variables; e, the elementary charge, α, the polarizability of the neutral, and μ, the reduced mass of the ion-neutral pair."\n\nclassical Langevin rate: k = 2πe √(α/μ)
903386
http://en.wikipedia.org/wiki/Hess%27_law
653659
Rate of Chemical reaction is defined as the amount of product formed per unit time or the disappearance of the reactant per unit time.
702349
http://www.ratemds.com/index.jsp
907845
The risk free rate is typically defined (in the US) as the Treasury rate.  However, it is not specified as to which maturity to look at.  If you are looking at a particular investment or corporate bond, I would recommend going with a Treasury rate having a similar maturity to the investment you're analyzing.\n\nThe Fed has a site called FRED (Federal Reserve Economic Data) with lots of info on it.  I've listed the site below, along with one where you can find interest rate data.  You can just look for the file that has a monthly frequency and then find the appropriate maturity.
340284
In excel:\n\n=RATE(12,65.33,-650) = 3.0076%\n\nFor the actual mathematical formula needed to solve this problem, the link below is pretty good:
642139
There's a article here: \n"The cutoff phenomenon in finite Markov chains"\n\nhttp://www-stat.stanford.edu/~cgates/PERSI/papers/cutoff.pdf
187632
The relative average deviation is the average deviation divided by the average of the measurements....lol\n\nIf that doesn't help much, check out the link below.\n\nMatt
96962
www.ratemyprofessor.com
309184
Beta is how much a stock moves compared with to the general market.  Its most common use off the top of my head is for calculating risk premiums to get a proper discount rate.  The different constants for WACC use the risk free rate added to beta multiplied by a risk premium.
168454
WilliamLCB is correct about the when.  The why is described in some detail at the Mathworld link below.  The summary is that dividing by (n-1) for the sample variance is required to give you a *unbiased* estimator for the population variance.
756392
"Kurtosis describes the concentration of data around the mean."\n\nkurtosis = 4th moment about the mean divided by the square of the 2nd moment about the mean (variance)\n\nkurtosis = (1/N)∑((Xi - M)/σ)^4, i=1 to N
679000
time= 2.303/(rate constant) log( initial conc / final conc)\n\nthis is for a first order reaction...
1047372
A hidden Markov model is a statistical model where the system being modeled is assumed to be a Markov process with unknown parameters.\n\nAn example *might* be the weather. We can measure temperature, windspeed, amount of rain, etc. and used these series of measurements to predict the next days weather. This assumes that tomorrows values depends on what happened today, or more generally on the past in a relatively simple way.
378935
adiabatic lapse rate?
207168
Try this:\nhttp://www.accessscience.com/Encyclopedia/3/37/Est_370700_frameset.html?doi
176116
A halflife is a form of time constant for characterizing exponential trends with a decay rate of 1/2. Another common time constant decay rate is 1/e.