In statistics, the standard deviation is a measure of the amount of variation or dispersion of a set of values. A low standard deviation indicates that the values tend to be close to the mean (also called the expected value) of the set, while a high standard deviation indicates that the values are spread out over a wider range.
Standard deviation may be abbreviated SD, and is most commonly represented in mathematical texts and equations by the lower case Greek letter sigma σ, for the population standard deviation, or the Latin letter s, for the sample standard deviation.The standard deviation of a random variable, sample, statistical population, data set, or probability distribution is the square root of its variance. It is algebraically simpler, though in practice, less robust than the average absolute deviation. A useful property of the standard deviation is that unlike the variance, it is expressed in the same unit as the data.
The standard deviation of a population or sample and the standard error of a statistic (e.g., of the sample mean) are quite different, but related. The sample mean's standard error is the standard deviation of the set of means that would be found by drawing an infinite number of repeated samples from the population and computing a mean for each sample. The mean's standard error turns out to equal the population standard deviation divided by the square root of the sample size, and is estimated by using the sample standard deviation divided by the square root of the sample size. For example, a poll's standard error (what is reported as the margin of error of the poll), is the expected standard deviation of the estimated mean if the same poll were to be conducted multiple times. Thus, the standard error estimates the standard deviation of an estimate, which itself measures how much the estimate depends on the particular sample that was taken from the population.
In science, it is common to report both the standard deviation of the data (as a summary statistic) and the standard error of the estimate (as a measure of potential error in the findings). By convention, only effects more than two standard errors away from a null expectation are considered "statistically significant", a safeguard against spurious conclusion that are really due to random sampling error.
When only a sample of data from a population is available, the term standard deviation of the sample or sample standard deviation can refer to either the above-mentioned quantity as applied to those data, or to a modified quantity that is an unbiased estimate of the population standard deviation (the standard deviation of the entire population).
Dear Fellows,
If we fit our data to a quadratic equation then What is meant by standard error for linear and quaratic coefficients ? I know that standard error is the standard deviation from the Sampling data. But for individual coefficients what is its interpretation ?
Best Wishes
Masood
I've worked in calibration for a few years and I know that my equipment has to be calibrated by a standard that is a certain amount more accurate than the piece of equipment I'm calibrating, but where exactly does it end where the most accurate piece of equipment is calibrated by the absolute...
In the standard model gravitron is a particle but Higgs boson is not. The Higgs field causes particles to acquire mass. Mass generates a gravitation field. Is gravitron is in any way related to Higgs boson? Is the Higgs field any way related to gravitation field?
my question is on part ii, my range ( as shown in the photo), is between 4.52 and 16.28, so my working would be (6+10+4+4)/(6+10+4+4+1) X100% ... the answer given is 72% which is differnt form my answer? which part of my working is wrong ?
I am presented a review of data which gives:
vapour pressures of a liquid have been measured and fit to the following equation:
Log10 (mmHg) = -3571/T + 8.999
The melting point has been determined to be 392.7 K.
A Cp value given for the liquid is 250 J/mol K
and the ΔSvap is 117 J/mol K...
Hi.
I've been reading that if one places a Dp brane in a 10d space then it's possible to have a string with [11] Chan-Paton index i.e. a string that starts and ends on the same Dp brane. Since the separation of the brane with itself is 0, this string corresponds to a massless particle. Why is...
What is the significance of the standard deviation (equal to the mean) in an exponential distribution? For example, as compared to the standard deviation in the normal distribution, which conforms to the '68-95-99.7' rule?
thanks
Homework Statement
Vapour pressures of a liquid have been measured and fit to the following equation:
Log10 P (mmHg) = -3571/T + 8.999
The melting point has been determined to be 392.7 K.
A Cp value given for the liquid is 250 J/mol K
and the ΔSvap is 117.20 J/mol K
Homework Equations...
Homework Statement
vapour pressures of a liquid have been measured and fit to the following equation:
Log10 (mmHg) = -3571/T + 6.124
The melting point has been determined to be 392.7 K.
A Cp value given for the liquid is 250 J/mol K
and theΔSvap is 117 J/mol K
Homework Equations...
Homework Statement
The vapour pressures of a liquid have been measured and fit to the following equation:
Log10 (mmHg) = -3571/T + 6.124
The melting point has been determined to be 392.7 K.
Calculate the standard entropy of the liquid at the melting point.
Homework Equations...
There are quite subtle gauge anomaly cancellations in the standard model.
Does anybody know a good summary about the algebraic constraints for number of fermions per generation, value of electroweak charges, etc.?
Hello
I am working on deriving the expression relating the equilibrium constant K to the change in Gibbs energy.
This part seems to be followed okay, but here
I am not following why the change in Gibbs energy of reaction is defined this way. I can see why K is defined in a way because...
Hello! I'm working on creating a sci-fi setting for a tactical space combat video game and short story series, and I had a few questions I couldn't find much info on after googling. I'll be playing a little bit loosely with the laws of physics for the sake of gameplay and storytelling, but I...
this is thing I'm thinking about for few years.
why standard passenger car diesel engines are so limited in engine capacities range?
if we take petrol engines, there are anything from 1.0 liter to 3.0l Inline 4 cylinders, 2.0-4.0l 6 cylinders (or even bigger in USA), 4-7l V8 etc.
but take...
In my previous two math classes I'd get the answer wrong if I put the number first then the variable as my answer. Now in this class this way of doing it is wrong. I'm seriously confused now. For instance the last two classes said that it was standard practice to write an answer like: 3x+4. This...
If thermodynamic temperature can be interpreted as the average kinetic energy in a system, is there a quantity defined as the standard deviation?
For example, let's say you poured some hot water into a cup of cold water. The instant you poured it the standard deviation of the system would be...
In the Gibbs free energy equation, does the standard change in entropy equal q(sys)/T(system)?
Or in math terms:
T(surr) * q(sys)/T(sys) = T(surr) * dS(standard)
Thus
dS(standard) = q(sys)/T(sys)
(surr) = surroundings
(sys) = systems
(standard) = at standard conditions
We're doing electrochemistry this week and this concept confuses greatly. I know that voltage is the work per unit charge. And electrons move from high potential(is this voltage as well?) to low potential- what is meant by this by the way? How is this related to standard reduction potential? If...
Homework Statement
Here is a slide in my notes:
I am kind of confused about mean and standard deviation. So in my notes it says X1 to Xn are independent measurements. Then it says each independent measurement has a mean μ. But how is this possible, if they are independent measurements (in...
good day everyone,
I wonder if anyone can direct me please on the international standard number or name that explain the safety and standard procedures in better distribution of power in breakers and panels from transformers.
in short, as I learned in my school and as best practice that...
In some textbooks ##\Delta \hat{x}## is called dispersion of coordinate ##\Delta \hat{x}=(\langle \hat{x^2} \rangle-\langle \hat{x} \rangle ^2)^{\frac{1}{2}}##. For me that is standard deviation. What do you think?
There are several ways to show the one-to-one correspondence between P(N) (= the power set of the natural numbers) and the set of the reals (or, equivalently, the set of reals in the interval [0,1).) Continued fractions, and all that. However, one argument is the following (sorry, this argument...
Hello
A manufacturer produces blocks of metal of
length 100 standard deviation 2,
width 200 standard deviation 1
depth 150 standard deviation 3
The mean volume will be 100x200x150 but what will its sd function be? (The figures I've given are just for clarity)
Thanks in advance...
Does anyone know what L is? I'm trying to see if I could find videos on it on YouTube.
On the first question this is what I think- [a;b] is a vector by the way:
1) [2;1]c1+[7;4]c2=[1;0]
[2;1]c1+[7;4]c2=[0;1]
I could have also combined those two by having the linear combination equal to a size...
Homework Statement
I have a set of values from a laboratory work (standard Additions practical), which I am required to plot. I am finding difficulties in plotting the values in excel because the horizontal axis must have some negative integers.
Homework Equations
The Attempt at a...
Homework Statement
For a certain random variable X, P(X≤500)=.5 and P(X>650)=.0227, find σ.
Homework Equations
μ=expected value=mean
Variance=∫(X-μ)2fx(X)dx evaluated from -∞ to ∞
σ=√Variance
The Attempt at a Solution
I'm not sure what the relationships between the...
Homework Statement
Let X1,X2,X3 be a random sample from a normal distribution with mean μ≠0 and variance σ2=1/24. What are the values of a and b, respectively, in order for L=aX1+4X2+bX3 to have standard normal distribution?Homework Equations
σ=1/√24
Converting normal distribution to...
I have an application where I need to find the density of a substance at standard conditions (101.325kPA, 15°C) from the density at recorded conditions (varies).
The first application is for natural gas at approximately 11Barg (160 psi, 1100kPA), 80°C (176°F).
The second application is for...
What is a Standard State or Reference State of an element?
Can someone please give me a simple explanation of what a standard state or reference state is? I don't quite understand the way wiki describes it which is -
The standard state, also known as reference state, of an element is...
In the standard model, the Lagrangian contains scalar and spinor and vector fields. But when we consider spontaneous symmetry breaking, we only account for the terms contain only scalar fields, " the scalar potential", in the Lagrangian. And if the scalar fields have vacuum expectation value...
Could you have a hypothetical universe with only photons, electrons, and positrons by adjusting the parameters of the Standard Model to eliminate all the "other" stuff?
If so is String Theory flexible enough to model a hypothetical universe with only photons, electrons, positrons, and...
Hello,
I am confused about the following scenario.
Suppose I have the reaction
CO (g) + 2H2 (g) → CH3OH (g)
and I am asked to solve for the heat of reaction at 800 C. My query is the following: when finding the heat of reaction at standard state, which heat of formation I should use...
This paper, http://arxiv.org/abs/1402.2717, discusses an alternative model for SN1a progenitors and offers observational predictions to test it based on SN2014J. If the model is validated it would have far reaching consequences for cosmology.
After filling out the table, I used it to finally calculate the standard deviation as 0.105. Just to make sure, I ran it through Microsoft Excel and got 0.942809042. I put two together and figured I'm doing something wrong after the xw column because Excel agrees that the mean is also 1.7...
Hi; I've been trying to solve the problem myself but i really don't what could be wrong;
The problem says :
Make the change of variables
x=ucos−vsin
y=usin+vcos
where the angle 0<(phi)<2 is chosen in order to eliminate the cross product term in
x^2+xy+y^2=6
Then find the standard form of...
I am a programmer and physics fan. A speaker (Lawrence Krauss?) at https://origins.asu.edu/events/great-debate-parallel-realities-probing-fundamental-physics (not on youtube yet) said physics theories beyond the standard model are an under-determined problem. There are 7,000 theories that fit...
Hello, PF!
[My question pertains to a non-rigorous, undergraduate introductory Probability and Statistics course. I'm no math major, so please correct me if I've mishandled any terms or concepts as I try to express myself. I'm always eager to learn!]
* * *
In a discussion of the...
I am a MSc student and I am looking for a place to do my PhD in Physics Beyond the Standard Model (Theoretical side). Any suggestions for a place to apply?. I know that there are the traditional elite places like MIT, Standford, Berkeley and so on but I am looking for other suggestions given...
Homework Statement
Graphite can be change into diamond according to the following equation:
Cgraphite ==> Cdiamond
Consider the following reaction equations:
Cgraphite + O2 (g) ==> CO2 (g) ΔH = -393.5 kJ/mol
Cdiamond + O2 (g) ==> CO2 (g) ΔH = -393.4 kJ/mol
Which form of...
I am wondering whether discussions of inflationary cosmology in these forums generally includes or explicitly excludes prior Plank era and GUT era dynamics. I never gave it any thought until reading the following.
The Wikipedia article provides a perspective I just don't remember from other...
For a set with n points of data, why is the "degree of freedom" of the standard variance n-1? Hell, what does "degree of freedom" actually mean?
Heck, my book "proves" this by saying that since ##\sum_1^n (x_i - \bar{x}) = 0## (obviously), then ##\sum_1^n (x_i - \bar{x})^2## must have n-1...
Hi all,
Would a heading of 330 degrees be equivalent to a standard angle measurement of 30 degrees? I'm used to calculating by subtracting the heading from 90, but the angle is too large for this problem. I know it seems to be a ridiculously simple question compared to others on this forum...
Studying for my proofs final right now...there's a problem on the study guide:
True or False. Assume standard properties of real numbers. Support your answers.
(a) For all \(x\) in the real numbers, there exists a \(y\) in the real numbers such that \(x+y>0\).
The answer: True. Given an \(x\)...
In Standard Hydrogen Electrode why only Platinum electrode should be used and why should it be dipped in HCl?why can't we use any other metal dipped in any other acid other than HCl?
Hi,,,can u please explain me how to calculate standard deviation and standard error for a binomial distribution when you have several samples?
For exapmple:
I don't know the population size. I take a sample of 10 and check for a particular characteristic. Let's say number of successes for this...
Hello all, I don't have a question on homework specifically, but I need clarification on something I'm reading in the textbook.
I will be starting an abstract algebra class in the spring and it's been quite a few years since I've had linear algebra, so I'll be reviewing that material before the...
I have a question regarding symmetry groups. I've often heard that the Standard Model is a SU(3) x SU(2) x U(1) theory. From what I understand these groups contain the symmetries under which the Lagrangian function is invariant. If so, what does every one of the 3 groups above contain (what...
I had this problem on a quiz and obviously got it wrong, I am confused about how to set this question up and what to solve for:
In a large city, the average retail price of a pound of grapes is $1.79, with a standard deviation of 18 cents. Between what values must be the price of at least 15/16...
In other words, can dark matter be reconciled with GR without drastically changing the idea that force is due to space-time curvature? and in the case of the standard model is there any thoughts of how the force of dark matter is transmitted via the exchange of a particle? It seems that this...