# 1.2 Machine learning lecture 3  (Page 8/14)

That’s the [inaudible] but, yes. You are assuming that the error has zero mean. Which is, yeah, right. I think later this quarter we get to some of the other things, but for now just think of this as a mathematically – it’s actually not an unreasonable assumption. I guess, in machine learning all the assumptions we make are almost never true in the absence sense,right? Because, for instance, housing prices are priced to dollars and cents, so the error will be – errors in prices are not continued as value random variables, because houses can only be priced at a certain number of dollars and a certain number of cents and you never have fractions of cents in housing prices. Whereas a Gaussian random variable would. So in that sense, assumptions we make are never “absolutely true,” but for practical purposes this is a accurate enough assumption that it’ll be useful to make. Okay? I think in a week or two, we’ll actually come back to selected more about the assumptions we make and when they help our learning algorithms and when they hurt our learning algorithms. We’ll say a bit more about it when we talk about generative and discriminative learning algorithms, like, in a week or two. Okay?

So let’s point out one bit of notation, which is that when I wrote this down I actually wrote P of YI given XI and then semicolon theta and I’m going to use this notation when we are not thinking of theta as a random variable. So in statistics, though, sometimes it’s called the frequentist’s point of view, where you think of there as being some, sort of, true value of theta that’s out there that’s generating the data say, but we don’t know what theta is, but theta is not a random vehicle, right? So it’s not like there’s some random value of theta out there. It’s that theta is – there’s some true value of theta out there. It’s just that we don’t know what the true value of theta is. So if theta is not a random variable, then I’m going to avoid writing P of YI given XI comma theta, because this would mean that probably of YI conditioned on X and theta and you can only condition on random variables. So at this part of the class where we’re taking sort of frequentist’s viewpoint rather than the Dasian viewpoint, in this part of class we’re thinking of theta not as a random variable, but just as something we’re trying to estimate and use the semicolon notation. So the way to read this is this is the probability of YI given XI and parameterized by theta. Okay? So you read the semicolon as parameterized by. And in the same way here, I’ll say YI given XI parameterized by theta is distributed Gaussian with that.

All right. So we’re gonna make one more assumption. Let’s assume that the error terms are IID, okay? Which stands for Independently and Identically Distributed. So it’s going to assume that the error terms are independent of each other, right? The identically distributed part just means that I’m assuming the outcome for the same Gaussian distribution or the same variance, but the more important part of is this is that I’m assuming that the epsilon I’s are independent of each other. Now, let’s talk about how to fit a model. The probability of Y given X parameterized by theta – I’m actually going to give this another name. I’m going to write this down and we’ll call this the likelihood of theta as the probability of Y given X parameterized by theta. And so this is going to be the product over my training set like that. Which is, in turn, going to be a product of those Gaussian densities that I wrote down just now, right? Okay?

where we get a research paper on Nano chemistry....?
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
Ali
what are the products of Nano chemistry?
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
hey
Giriraj
Preparation and Applications of Nanomaterial for Drug Delivery
revolt
da
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
ya I also want to know the raman spectra
Bhagvanji
I only see partial conversation and what's the question here!
what about nanotechnology for water purification
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
why we need to study biomolecules, molecular biology in nanotechnology?
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
why?
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
how did you get the value of 2000N.What calculations are needed to arrive at it
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