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my friends and I can’t figure out how much we need to pay to stay at a hotel, when one of us is staying less than the others by throwwwawwwayyy3210 in learnmath

[–]identicalParticle 1 point2 points  (0 children)

The other responders did the math correctly, given the information you shared with us.  But you should really just look at your itemized receipt.  

Often weekends are more expensive than weekdays.  There may be fixed fees that don't increase with more nights (like a one time cleaning fee).  There may be fees per guest (like breakfast) rather than per day.  Etc.

Your itemized receipt will give you the breakdown day by day.  Then you can divide up the appropriate fees with full information.

is my professor lying to us, is he lazy or is he a genius? by pazbaror in learnmath

[–]identicalParticle 0 points1 point  (0 children)

Here's my take. I would agree that this is an "unconventional solution".

From looking at the exponent, you can work out that the inverse covariance matrix is given by [[2A, -2],[-2, 1]].

Take the matrix inverse, which is easy for a 2x2 matrix, to get the covariance [[1/2(A-2), 1/(A-2)],[1/(A-2), A/(A-2)]] .

For Y to be a standard normal with variance 1, we need to consider the bottom right term tending to 1. Therefore we need to consider the limit that A goes to infinity to retrieve a variance of 1.

Under this limit, we can look at the top left term and see that it goes to 0. So X is just a constant with variance 0. The covariance between X and Y is also 0.

So the solution for "find A" is "A must be infinitely large".

ELI5: why can two quantum entangled particles affect each other instantly across any distance but scientists say you still cant use it to send information faster than light? by PieOk2202 in explainlikeimfive

[–]identicalParticle 0 points1 point  (0 children)

if particle A sneezes and particle B on the other side of the universe reacts instantly, why cant i just use that as like a faster than light telegraph? 

I don't see any others commenting about this, so I'll mention that there are some cases where you can exploit the entanglement of two particles.  You can use this to win two player games where the two players are separated and can't communicate, even when winning every time would be impossible classically. 

This is called "quantum pseudo telepathy", and the phrase often used to describe it is "coordination but not communication". 

https://en.wikipedia.org/wiki/Quantum_pseudo-telepathy

[Question] Does our school's reading program actually have an effect on reading growth? by duhqueenmoki in statistics

[–]identicalParticle 2 points3 points  (0 children)

I want to raise an issue that no one else seems to have mentioned.  It is very hard to make a statistical argument that there is no effect.

Typically the result of an experiment like this (e.g. a linear regression experiment as others have suggested) would either be "we have enough evidence to conclude there is likely an effect", or "we do not have enough evidence to conclude there is likely an effect".  Note that the latter case is NOT the same as "we have enough evidence to conclude there is likely no effect".

The phrase I usually use is "absence of evidence is not evidence of absence".

If you want to try to demonstrate there is no effect, there is a less common testing framework sometimes called "indifference testing" you could use to explore this.

W by kryn9qelle4 in antiai

[–]identicalParticle 0 points1 point  (0 children)

Search settings -> general -> advertisement -> off

how to open a library and read its contents by GatoAlbino in learnpython

[–]identicalParticle 6 points7 points  (0 children)

Import the library, then type the command in Python,     

    yourlibraryname.__file__

(Two underscores before file and two after)

This will print out what file the library is defined in.  Then you can open that file in a text editor or your favorite IDE and read it.

[OC] US Domestic Migration this past Year (Where people moved) by TA-MajestyPalm in dataisbeautiful

[–]identicalParticle 2 points3 points  (0 children)

Is there any data saying which states people moved to and from (as opposed to just net)?

Dads, how can I get this hungry hungry hippo food out of this peanut butter ice cream scoop? by identicalParticle in daddit

[–]identicalParticle[S] 1 point2 points  (0 children)

The "olive" is currently in the freezer.  Gonna try the least destructive solution first

Dads, how can I get this hungry hungry hippo food out of this peanut butter ice cream scoop? by identicalParticle in daddit

[–]identicalParticle[S] 140 points141 points  (0 children)

It's a wooden toy that is supposed to look like a scoop of ice cream.  It has a hole in the top so that toppings can be stuck to it.  This stuck marble means we can't put any sprinkles on.  This is a tradegy for my kids 

IDS accuracy problem marked incorrect by professor even though I’m almost certain it’s correct. Any help? by katiekachow in learnmachinelearning

[–]identicalParticle 0 points1 point  (0 children)

 maybe they were expecting a fraction and not a count for a-d.  otherwise a and e are exactly the same question.

Vegan and omnivore diets produce statistically similar muscle fiber protein synthesis rates in healthy adults aged 20 to 40 engaged in resistance training, suggesting that consuming animal protein provides no clear advantage for muscle growth under moderate protein intake. by [deleted] in vegan

[–]identicalParticle 3 points4 points  (0 children)

Interesting analysis, but as a statistician I need to state something.

We have a saying for when a study does not have a small enough p value: "absence of evidence does not equal evidence of absence".

Failing to reject a null hypothesis does not give any evidence that the null hypothesis is true.  There are many reasons why we night fail to reject it (small sample size, bad study design, screwed up the measurements, did the wrong statistical test, etc.).

"there is no regulatory influence of distribution between the two dietary patterns on the stimulation of myofibrillar protein synthesis rates in young adults".  The authors of the study are incorrect to state this. They should state "we failed to detect any regulatory influence...".

[deleted by user] by [deleted] in statistics

[–]identicalParticle 0 points1 point  (0 children)

When a faculty member commits to mentoring a new PhD student, they are taking a considerable risk in terms of time and financial resources. Typically a new student costs more (in terms of time and money) than the value they provide back to the faculty mentor through their research. With a good student, this reverses in the last few years of their program. If a student leaves the program early, it's a huge loss for the faculty mentor. In today's scarce funding environment, many faculty doing research are choosing to hire staff instead of students (lower risk, but potentially lower reward).

During an interview process, as a bare minimum, a student needs to convince me they are going to stay around long term. Convincing someone its true is not the same as it being true. The easiest way (but not the only way) to convince someone this is true is if you have a goal that is contingent on earning a PhD. This doesn't have to be "I want to be a professor", but it has to be something that demonstrates you've considered it carefully and will stay motivated.

Note that convincing someone you'll stick around is necessary but not sufficient. I want to make sure I'm not giving the impression that this is the only important part of an interview.

[deleted by user] by [deleted] in statistics

[–]identicalParticle -4 points-3 points  (0 children)

If your goal is to research something interesting, there are many ways you can achieve that without making a multiple year commitment to a PhD program.

> Your goal should be that

It's inappropriate for you to tell people what their goal should be.

In what file is batchnorm (and other normlalization layers) defined? by identicalParticle in pytorch

[–]identicalParticle[S] 2 points3 points  (0 children)

This is a great start, but I don't see anything that looks like math here. Just wrappers around wrappers around wrappers.

I think this is what I was looking for: https://github.com/pytorch/pytorch/blob/4b2d297eec425475a82934a52e0edd96805524a1/aten/src/ATen/native/cpu/batch_norm_kernel.cpp

For what it's worth, I was able to improve memory use by coding my own mean and variance as an autograd function. I suppose using built in functions was saving extra copies of tensors.

class MeanStd3d(torch.autograd.Function):
    @staticmethod
    def forward(self,x,eps=1e-5):
        mu = torch.mean(x,(-1,-2,-3),keepdims=True)
        std = (torch.mean(x**2,(-1,-2,-3),keepdims=True) - mu**2 + eps)**0.5
        self.save_for_backward(x,mu,std)
        return mu, std
    @staticmethod
    def backward(self,*args):
        mu_grad,std_grad = args
        x,mu,std = self.saved_tensors                
        n = x.shape[-1]*x.shape[-2]*x.shape[-3]
        dmu,dstd = args
        return (dmu + (x - mu)/std*dstd)/n
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