Thought I would follow up here and try to more succinctly describe the problem. At its core, I have three random variables that are normally distributed:
x_1 \sim N(\mu_1, \sigma_1) \\
x_2 \sim N(\mu_2, \sigma_2) \\
x_3 \sim N(\mu_3, \sigma_3)
I also know there is a relationship among...
Thanks for the reply. I do check assumptions about distributions with high-stat simulations to try and catch mistakes. In the situation I'm describing above, it is the high-stat sims that show I must be doing something wrong... but not horribly so. I have both a bias in my final results as...
I run into this issue with my research when modeling particle detector responses with a normal distribution since it will on occasion try to produce a negative energy particle (clearly not realistic). There are options but they produce biases. One is to just cap the low end at zero (or nearly...
Hello PF! It's been a while. How are things?
In my research I'm faced with determining a probability distribution from a function built as follows:
Perform three measurements X, Y, Z that have normally distributed errors.
Impose a constraint and variable change that allows me to...
Sometimes you can get in (not top tier) with less than 3.0 on probation. Your scores on the Physics GRE would probably be a primary factor.
Depending on the school you may even hedge your bet a little and apply for M.S. program, then move on to the Ph.D. after a couple semesters once you've...
I suppose that depends. Are you still an undergrad? In grad school? If an undergrad, taking classes certainly wouldn't hurt. Full disclosure: I have degrees in both comp sci and physics so I'm biased. I have found the comp sci background to be extremely useful since I encounter multiple...
Yes, yes, and yes. Those three are a good start ;) C++ and Java are very close in structure and syntax, so not a big deal to know both. Python is just, well, awesome. Ok, not in all aspects, but for certain things (fast prototyping of an idea) it is. Plus it's really easy to learn.
Your situation sounds very familiar. My first degree was Computer Science. I actually went back to get an undergrad in Physics before going on to grad school. It took four semesters because of the class sequence (I also picked up a math degree while I was at it).
In my school, IF one...
If I understand the definition correctly, then I think so. Y, A, B, C are normally distributed about a mean, but not necessarily independent (i.e. covariance != 0).
A thought I had was to perform principle component analysis on A, B, C so I then would have some new (independent) eigenvectors...
You are correct, I am looking to calculate the expected value of Y given A, B, C and known correlations YA, YB, YC, AB, AC, BC (and necessary variances, etc...)
I've searched the forums but am unable to find an answer to this:
Given two variables with a correlation, you can predict one from the other using the familiar
E(Y|X) = EY + r * s_y * (X - EX) / s_x
What I want to know is how to predict values from multiple variables, especially when these...
I very briefly did some exploration working directly with OpenGL, but it seemed like a ton of work to handle things at that level. So then I learned 3D in Java using java3d. I found a tutorial and very diligently followed it step by step. A few days in, I was able to do some cool stuff from...
I am facing an issue in my research where I need to enumerate all combinations of an underlying set. BUT the set has some special features. Here is an example:
Given a set {A,B,C,D,E, F} where each item in the set consists of two values. Something like:
A = (1,2)
B = (3,4)
C = (5,6)...
It's true, lepton-lepton collisions are much nicer to deal with. Plus *all* center of mass beam energy is available to make a particle (which is generally not the case for hadrons). You need to have much more energy in your hadron beam than the energy of physics you are actually exploring...
Centripetal acceleration is acceleration directed towards the center of circular motion. So this is usually
a_c=-\omega^2 r
or
a_c=-\frac{v^2}{r}.
In either case you need to know how fast the disc is rotating (and its radius). So how would you determine how fast the disc is...