# Questions tagged [descriptive-statistics]

The area of statistics that provides descriptions of data, may it be samples or the population. This includes graphical representations and numerical indicators. No information is inferred from samples about the population, as in inferential statistics.

13 questions
7k views

### Why is variance squared?

The mean absolute deviation is: $$\dfrac{\sum_{i=1}^{n}|x_i-\bar x|}{n}$$ The variance is: $$\dfrac{\sum_{i=1}^{n}(x_i-\bar x)^2}{n-1}$$ So the mean deviation and the variance are ...
1k views

### Minimal sufficient statistic of $\operatorname{Uniform}(-\theta,\theta)$

I am seeking clarification on why both the vector $(X_{(1)},X_{(n)})^T$ and $\max\{-X_{(1)},X_{(n)}\}$ are sufficient for $\operatorname{Unif}(-\theta,\theta)$, but only $\max\{-X_{(1)},X_{(n)}\}$ is ...
144 views

### How can the median number of sexual partners be 6.1 and 3.6?

http://www.cdc.gov/nchs/nsfg/key_statistics/n.htm Median number of female sexual partners in lifetime, for men 25-44 years of age, 2006-2008: 6.1 Wouldn't it only be able to be x.5 or x.0?
704 views

### Interpreting the scatter plots of two random variables

Suppose I sample random variables A and B from normal distributions. When I do a scatter plot of these two variables I see a ...
809 views

### Correctness of a statistical evaluation of a parameter

I have a question about a non-Gaussian distributed parameter that can only take certain values in a defined interval. Knowing that I have to define this parameter starting from a set of its values and ...
73 views

### Is there any meaning of this “Median-mean”

Given a data set $\{a_1,\cdots,a_n\}$ with median M Define the medimean to be the value of $x$ s.t. $$\left(\frac{1}{n}\sum_{n}{}{a_n}^x \right)^{1/x}=M$$ Is this $x$ value useful / used at all in ...
156 views

### 'Weighted' Markov Chain Statistics

Let $\mathbf{X} = (X_0, X_1, ..., X_n)$ be a finite length walk on a Markov chain with initial distribution $\lambda$, transition matrix $P$, over the state space $\Omega = \{1, 2, ..., l\}$. Suppose ...
231 views

### Why minimising the MSE in Variance-Bias tradeoff?

As I understand the Variance-Bias tradeoff, modifying estimators to minimise bias might increase the variance of the estimator and vice-versa. For the simple case of the biased variance estimator, ...
932 views

### What is Expected Prediction Error (EPE) a function of?

Context I am self-studying Elements of Statistical Learning (2nd ed), by Friedman, Hastie & Tibshirani. I have a question with regards to what the EPE, as defined in this text, is a function of. ...
124 views

### Which mean is used for standard error?

While calculating the standard error, we take the standard deviation of the sampling distribution. But for calculating the standard deviation we must consider a 'mean' to take difference about. In ...
840 views

### MLE of variance minimising the mean squared error

While reading up on the derivation of a Maximum Likelihood Estimator for population variance, the MLE for Variance ends up being the biased sample variance, $\frac{n-1}{n}S^2$ where $S^2$ is the ...