# Tagged Questions

Creating samples from a well-specified population using a probabilistic method and/or producing random numbers from a specified distribution.

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### I have a discrete distribution and want to know to what extent other samples differ from it, what is the right test?

This is kind of a basic stats question, but I want to make sure I am doing this right. I have a distribution of objects. Specifically: ...
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### Does sampling error include measurement error?

Gross sampling error (MSE) appears to be a composite of two errors sampling and measurement error. How do we assess measurement error ? can we find out net sampling error ?
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### Convergence theorem for Gibbs sampling

The convergence theorem for Gibbs sampling states: Given a random Vektor $X$ with $X_1,X_2,...X_K$ and the knowlegde about the conditional distribution of $X_k$ we can find the actual distribution ...
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### Performing binary logistic regression with equal number of cases and non-cases

The best way to ask my question is to present an example scenario: Let's say that the outcome of interest is lung cancer (1 = lung cancer; 0 = no lung cancer) and a researcher has 200k records (where ...
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### Sub sampling a dataset without losing the distribution

Suppose that I have a huge data set with high number of dimensions (components). For computational purposes I would like to take just a sample of this data set and work with it instead of working with ...
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### Probability of pairwise difference of samples from distribution with finite support

I'd appreciate any help on the following problem: Let $X_1, X_2, \dots, X_N$ be i.i.d. continuous random variables with support $[0, 1]$. What is a reasonable bound on the probability that some pair ...
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### How to combine data from 5 surveys from the same population spanning 10 years

I have results from 5 surveys each 2 years apart and let us assume that no subjects are selected in more than one survey. The sampling method used in these surveys are biased and I have sampling ...
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### How to deal with non random samples?

I have a specific question about random selection, representativeness and inference. It is well known that it's necessary to use random selection to get representative samples from the population of ...
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### Determining sample size when given %C.I. and margin of error in a finite population

I'm trying to determine n, the sample size. We have $N=580$ and we want to estimate population proportion, $p$, at a 95%-CI and a margin of error of $0.10$, then I get $$n=Npq / (N-1)D + pq$$ ...
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### Randomized Results Sampling

I'm taking a look at randomized results and have a question about an end case. Specifically, suppose my scheme is as follows: 1) I want to ask question Q_A. The probability of answering Q_A in the ...
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### Generalizing results from a sample

I have the following exercise question that I would like insight on: A legal case is being formulated by a union of secretaries who claim that they are being paid unfairly low wages by their ...
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### Estimating the confidence interval in a convenience sample

So there's a textbook question I stumbled upon: A marketing research firm estimates the proportion of potential customers preferring a certain brand of lipstick by "randomly" selecting 100 women who ...
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### Show $\mathrm{V}(\bar{y}) = \sigma^2/n\cdot (N-n)/(N-1)$

How do we show that $$\mathrm{V}(\bar{y}) = \frac{\sigma^2}{n}\cdot \frac{(N-n)}{(N-1)}$$ I think this is the sample variance for simple random sampling without replacement. I have not seen this ...
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### How to get sampling size (Ecology)

I wanted to ask how to get the sampling size for an area sampling? We are about to survey the moss genera present in a specific area. The area is around 50 hectares. We can't observe the whole area. ...
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### How to impute or predict a characteristic when one of the IVs in the prediction is other household members having that same characteristic?

In some data set A, we have: household id, person id, age, sex, and then a simple binary likes donuts / does not like donuts variable. In some other data set B, we ...
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### Gibbs sampling in document clustering

I'm trying to understand the idea behind the Topic Models in document clustering. In Latent Dirichlet Allocation, it is necessary to approximate the posterior distribution of topics over the document. ...
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### Why do two equivalent approaches to selecting numbers that sum to 100 produce different results

This question is inspired by two seemingly equivalent attempts to solve a question asked yesterday: In R, how to sample from the output of combn(a,b) if the "a choose b" is too large? ...
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### How to testing the probability of two factors being found together?

I know how many times a particular factors has been found: values<-cbind(f=c("S1","S10","S3","S4","S5","S6","S7","S8","S9"),count=c(9,8,4,24,20,4,8,21,5)) I ...