# 7.8 Central limit theorem: summary of formulas

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Formula

## Central limit theorem for sample means

$\overline{X}$ ~ $N\left({\mu }_{X},\frac{{\sigma }_{X}}{\sqrt{n}}\right)\phantom{\rule{35pt}{0ex}}$ The Mean $\left(\overline{X}\right)$ : $\phantom{\rule{10pt}{0ex}}{\mu }_{X}$

Formula

## Central limit theorem for sample means z-score and standard error of the mean

$z=\frac{\overline{x}-{\mu }_{X}}{\left(\frac{{\sigma }_{X}}{\sqrt{n}}\right)}\phantom{\rule{25pt}{0ex}}$ Standard Error of the Mean (Standard Deviation $\left(\overline{X}\right)$ ): $\phantom{\rule{10pt}{0ex}}\frac{{\sigma }_{X}}{\sqrt{n}}$

Formula

## Central limit theorem for sums

$\mathrm{\Sigma X}$ ~ $N\left[\left(n\right)\cdot {\mu }_{X},\sqrt{n}\cdot {\sigma }_{X}\right]\phantom{\rule{10pt}{0ex}}$ Mean for Sums $\left(\mathrm{\Sigma X}\right)$ : $\phantom{\rule{10pt}{0ex}}n\cdot {\mu }_{X}$

Formula

## Central limit theorem for sums z-score and standard deviation for sums

$z=\frac{\mathrm{\Sigma x}-n\cdot {\mu }_{X}}{\sqrt{n}\cdot {\sigma }_{X}}\phantom{\rule{25pt}{0ex}}$ Standard Deviation for Sums $\left(\mathrm{\Sigma X}\right)$ : $\phantom{\rule{25pt}{0ex}}\sqrt{n}\cdot {\sigma }_{X}$

## Average

• A number that describes the central tendency of the data. There are a number of specialized averages, including the arithmetic mean, weighted mean, median, mode, and geometric mean.

## Central limit theorem

• Given a random variable (RV) with known mean μ and known standard deviation σ. We are sampling with size n and we are interested in two new RVs - the sample mean, $\overline{x}$ , and the sample sum, ΣX.If the size n of the sample is sufficiently large, then $\overline{X}$ ~ $N\left({\mu }_{X},\frac{{\sigma }_{X}}{\sqrt{n}}\right)$ and $\mathrm{\Sigma X}$ ~ $N\left(n\cdot {\mu }_{X},\sqrt{n}\cdot {\sigma }_{X}\right)$ . If the size n of the sample is sufficiently large, then the distribution of the sample means and the distribution of the sample sums will approximate a normal distribution regardless of the shape of the population. The mean of the sample means will equal the population mean and the mean of the sample sums will equal n times the population mean. The standard deviation of the distribution of the sample means,, is called the standard error of the mean

## Mean

• A number that measures the central tendency. A common name for mean is 'average.' The term 'mean' is a shortened form of 'arithmetic mean.' By definition, the mean for a sample (denoted by $\overline{x}$ ) is $\overline{x}$ (the sum of all values in the sample divided by the number of values in the sample), and the mean for a population (denoted byμ) is μ (the sum of all the values in the population divided by the number of values in the population).

## Standard error of the mean

• The standard deviation of the distribution of the sample means, $\frac{{\sigma }_{}}{\sqrt{n}}$

anyone know any internet site where one can find nanotechnology papers?
research.net
kanaga
Introduction about quantum dots in nanotechnology
what does nano mean?
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
it is a goid question and i want to know the answer as well
Maciej
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
for screen printed electrodes ?
SUYASH
What is lattice structure?
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
what's the easiest and fastest way to the synthesize AgNP?
China
Cied
types of nano material
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
how did you get the value of 2000N.What calculations are needed to arrive at it
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