# standard

1. ### Standard deviation on scaling of random variables

I have the answer already (based on simulations), but want to know exactly which theorem/ law is at play: Suppose X1, X2, X3, X4 are 4 positive random variables such that X1+X2+X3+X4=1. Suppose I scale them with known constants C1, C2, C3, C4, respectively, then look at the function below...
2. ### Mean of means - standard deviation of mean values

Sorry if this has been asked numerous times and sorry if I describe it from an engineers point of view. Let us say I have N measurements and I calculate the mean value and the standard deviation. Okay. Now let us have M times N measurements. I could calculate now the mean value of the whole...
3. ### Criticism of the Standard Deviation

Standard Deviation is widely used to measure risk in assets. I think a higher standard deviation is considered a risky bet, with greater upside and downside potential. However, if the asset A's returns are: 50, 50, 50, 400 and Asset B's return are 50, 50, 50, 50 -- the latter will have much...
4. ### Confidence interval for the population standard deviation?

Use the given degree of confidence and sample data to find a confidence interval for the population standard deviation. Assume that the population has a normal distribution. The hockey coach selected eight players at random and timed how long each player took to finish their exercises. The...
5. ### Standard Deviations and Standard Deviations of Reciprocals

If the standard deviation of A, B, and C is greater than the standard deviation of X, Y, and Z, what does that say about the standard deviation of 1/A, 1/B, and 1/C compared to the standard deviation of 1/X, 1/Y, and 1/Z? A, B, C, X, Y, and Z are rational numbers > 1.
6. ### Unbiased Estimator of the Standard Error of another Estimator

Suppose that $Y_1,...,Y_n$ is an IID sample from a uniform $U(\theta, 1)$ distribution. The method of moments estimator for $\theta$ is $\tilde \theta=2\bar Y-1$. The standard error of $\tilde \theta$ is $$\sigma_{\tilde \theta}=\frac{1-\theta}{\sqrt{3n}}$$ Find an unbiased estimator of...
7. ### Why use variance instead of standard deviation?

This drives me crazy, The question is simple: A manufacturing process has the expected value of 200minutes and standard deviation of 10minutes The reset process has the expected value of 30 minutes with the standard deviation 3 minutes Compute the probability that the sum of the...
8. ### Manipulate data to match given mean and standard deviation

I have a set of data with a mean of 55.05 and a standard deviation of 7.51. However, I want to transform these data to a list of values with a mean of 55.62, a standard deviation of 58.69, and the list should not contain negative values. Is this possible? Thank you The list of data is below...

18. ### Standard Deviation

What is approximate standard deviation for the list of numbers: 10.4, 9.8, 10.0, 9.2, 10.5, 9.8, 9.9, 10.1, 10.4, 10.2, 10.7, 9.6? A. 2.1 B. 1.9 C. 1.75 D. 1.8 The question shows up on my kid's test recently. The standard deviation is 0.42. Why can the answer be C. 1.75? If 0.42...
19. ### Conic Section Parabola Standard Form

Can someone check my work? If I did wrong please explain to me how to do it right? I only googled how to do it and that's how I've come up with that answers, based on this..
20. ### Dividing Standard deviation by sqrt(n)

Hi all, I've been arguing with a mate about a thing he calls Real Standard Deviation. What he does is siply dividing the standard deviation of a set of data by the square root of the number of observations, n. Now, I myself couldn't find any information about it on google, and can't really...