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

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Adjusting Probability for oversampling

I am developing a marketing (Churn) model that has an event rate of 0.5%. So i thought to perform oversampling. I mean making the number of events equal to number of non-events by reducing non-events ...
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13 views

representative samples formula [on hold]

I have just started working in quality management and I need to work out a representative sample of a given population of inputs needed for our production to assess them i.e if the bottles we get ...
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28 views

Analysis with unequal starting groups

Background: Our business wishes to perform an demand analysis based on two marketing treatments A and B. Due to constraints imposed from the onset, there will be a 50/50 split (receive/not-receive) ...
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28 views

Samples needed for variance accuracy [on hold]

How many samples should one take to guarantee $n$ digits of accuracy ($n$ digits total digits both before and after decimal Eg: truncating $412.243$ to $2$ digits is $410.000$ while truncating to $5$ ...
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20 views

How to convert World Fertility Surveys 1975’ raw data-DAT files into a set of Stata dta files [closed]

How to convert World Fertility Surveys 1975’ (for Pakistan) raw data-DAT files into a set of Stata/SPSS data files. I have found this link but this didn't work Turning the World Fertility Surveys’ raw ...
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1answer
46 views

How to simulate more data for machine learning?

I am attempting to analyze a small dataset using machine learning (SVM, binary problem). There are $103$ samples and $215$ variables (all variables are real numbers). Some of the variables (around ...
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43 views

Is weighing cases allowed/necessary for the Kruskal-Wallis and its post-hoc tests?

I have a dataset where I have respondents from 3 different countries (USA, NL & DE) and use the Kruskal-Wallis to determine if there are any statistically significant differences regarding ...
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1answer
111 views

How to test is social structure is a result of genetic relatedness whereas include the demography effect

I am trying to construct (undirected) social network based on co-occurence of individuals. Clustering algorithm will be later applied on this network to find some distinct subgroups. Issue is that ...
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49 views

Sampling from an (almost) multivariate normal over matrices

Consider $n$ points in the euclidean plane, $p_i = (x_i,y_i)_{1\leq i \leq n}$. Now consider a $2 \times 2$ matrix $M = \left(\begin{array}{cc}a & b\\c& d\end{array}\right)$ a vector $r = ...
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21 views

How to call extreme samples in a Monte Carlo simulation for hypothesis testing?

For many hypothesis tests, Monte Carlo methods are used to estimate the empirical $p$-value which is defined as $$p=\#{(T_{sample} > T_{observed})}/N.$$ Is there a name for the samples with ...
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10 views

how to calculate sample size for quasi experimental non equivalent pretest post test design where p is not known?

I am conducting a study with one treatment group and 2 comparison groups on tobacco cessation among school children in india. The GYTS 2009 has measured intention but there is no data available on % ...
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2answers
29 views

In survey sampling, have calibration margins to be known (estimated with 0 variance)?

Calibration estimators in survey sampling (as defined by Deville and Särndal, and implemented for example in the SAS macro "Calmar") generalize many other calibration estimators, including ...
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58 views

Stratified Random Sampling Implementation how to in R?

I have a dataset of 20 million rows. it is organized into strata (groups), and I need to sample from them. I need to create a smaller sampled dataset on which I bulid a regression model. I need to ...
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28 views

Justify sample size of 30 per group is valid

I am conducting a quasi experimental study. Both my control and study groups consist of 30 participants. I wasn't able to compute for the effect size etc. beforehand. Please help me to justify that 30 ...
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42 views

Bounding the bias of standard deviation estimate for stratified sampling (MC)

I cannot find an answer to this issue: in Monte Carlo runs, if one uses stratified sampling then the unknown bias of the variance estimator ( $\bar{\sigma}^2=\frac{1}{N}\sum{(y_i-\bar\mu_y)}$ where ...
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1answer
28 views

The design effect

The design effect (deff) quantifies the extent to which the expected sampling error in a survey departs from the sampling error that can be expected under simple random sampling . My question is ...
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61 views

Consequence of violation of independence assumption on estimates of standard errors

from the first chapter , Introduction to Multilevel Analysis , p.5 of the book , it is written that : Standard statistical tests lean heavily on the assumption of independence of the ...
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95 views

Is the accessible population a random sample?

At academic institutions dedicated to teaching we often use our current students taking a specific class, the accessible population, as a random sample when our actual sample includes all students who ...
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1answer
20 views

Can you use event history analysis if your sample was selected on the dependent variable?

I have a dataset that includes a random sample of individuals who are currently in a relationship in the United States. I also have data on the date that they met their partner and the date that they ...
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1answer
16 views

Information content of a set of random variables

Suppose there is some distribution $F$ not known to us. However, we can get information about this distribution by means of samples, i.e. we have a set of random variables from this distribution. ...
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3answers
188 views

Using Uniform Distribution to Generate Correlated Random Samples in R

[On recent questions I was looking into generating random vectors in R, and I wanted to share that "research" as an independent Q&A on a specific point.] Generating random data with correlation ...
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12 views

Binary variance? Comparing two sacks of uneven coins or two heterogenous groups of people

I have two sacks of coins. In one sack, the coins are all uniform, each giving a fairly constant 0.5 chance of heads (based on tossing a few of them and also visual inspection). I then estimate the ...
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54 views

Poor sample measurement and the Central Limit Theorem

I have a fairly basic question about the Central Limit Theorem. I understand it in principle, but I like to know specifically what happens when there is poor measurement on the samples. Say for ...
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2answers
37 views

How was public opinion survey sampling done in early 20th century?

The question is motivated by reading about Gallup's success in predicting the 1936 US election with a much smaller but more representative sample than Literary Digest. Literary Digest used phone ...
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1answer
26 views

How to sample from a non-parametric density estimate?

I have a kernel based non-parametric distribution, let's assume it's a Normal kernel, but the variance of each component is different. How do I sample from this density? If all the components had the ...
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30 views

Kurtosis of linear combination of independent variables

Dear fellow statisticians, mathematicians, I struggle to find proof of one seemingly simple statement. I would be very grateful for any help, I am quite desperate finding the proof. I thank you very ...
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36 views

Are Latin hypercube samples uncorrelated

I understand the basics to Latin hypercube sampling, such as implemented by the algorithm LHSA mentioned in the book Design and Modeling for Computer Experiments. But I'd like to make sure: 1, n ...
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41 views

Calculating needed sample size for two stage stratified cluster sample

We want to carry out a survey to assess perceptions of quality and access to medical education of last year students. Based on our research, we have decided that a two stage stratified cluster sample ...
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1answer
255 views

Molecules movement distribution puzzle

Let's say I have blood samples of whiteblood cells ($x$) and viruses ($v$). Space has been discretized in $LL$ spaces. They have a $p_v$ probability of interacting when found in the same space. I want ...
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2answers
28 views

Sampling distributions of sample means

Given a population from which we draw repeated samples of fixed size, say, 'n', my questions is what size is considerable? Is there any lower bound on sample size? Also how many such samples do we ...
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28 views

Is it better to use a random sample with 15% response rate or quota sample?

If I use a random sample, it will mean a 15% response rate for around 400 responses. If I use quota sampling using an existing online panel that is representative of the UK population by age, gender ...
3
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1answer
24 views

sample from a von Mises distribution by transforming a RV?

Is there a distribution $p$ that I can sample from, such that for $\epsilon \sim p$, and for closed-form deterministic function $g_{\mu,\kappa}$, $g_{\mu, \kappa}(\epsilon) \sim ...
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14 views

Comparing effect sizes of two treatments from a large number of studies

I suppose this would be some kind of meta-analysis. I would like to compare the effect sizes of two treatments from a large number of published studies. I would like to show that the other treatment ...
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2answers
34 views

Distribution of p(x) in empirical model

I am having a hard time to exactly name what I am looking for (I am quite sure it already exists out there...) so I'll start with a concrete example: I have a population of discrete colours (red, ...
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1answer
104 views

Sampling from Dirichlet-Multinomial

How do I sample from a Dirichlet-Multinomial distribution. One which has this pmf: http://en.wikipedia.org/wiki/Dirichlet-multinomial_distribution#For_a_multinomial_distribution_over_category_counts
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1answer
37 views

extrapolation and selection bias

I have a cohort of patient data. I have 100 Affected and 900 UnAffected I am reassessing one of the variables for each of the patients, however I can only do so for 90 Affected and 200 UnAffected. ...
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10 views

Sampling comparison groups based proportionality versus real-world frequency

I am looking at differential gene expression (using a t-test) in the context of five Breast Cancer Subtypes. I am working with data in which the distribution of subtypes matches real-world frequency ...
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2answers
59 views

Applying inferential statistics for census data

Let's assume I have a census data of a population which I would like to study and it has variables such as age, gender, sex, occupation etc and the dependent variable which is community participation ...
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1answer
530 views

Which formula is this?

I'm enrolled in a statistics course and missed a few classes so need help in deciphering this formula from a friend's notes. Sorry if this seems a very basic question. I know the formula is somehow ...
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1answer
31 views

What role does the sampling fraction play in the simple random sample variance formula?

Consider a survey where the population being estimated is finite. Using a simple random sample, you draw $n<N$ data. The sampling fraction is $f=\frac{n}{N}$. The variance will be ...
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18 views

Controls sampled on confounding variable

Let's say I wanted to use logistic regression to analyze the effect of an exposure variable on a categorical outcome variable ("yes" or "no"). I believe there are two important confounding variables ...
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61 views

Gibbs sampling for reducible chain

I am new to Gibbs sampling and I ran into a problem with irreducibility. For the Gibbs sampler to work the Markov chain has to be irreducible. But that assumption is not satisfied in my probability ...
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28 views

Sampling from Study Population for Labeling

I have the opportunity to get labels for a portion of my study population, and I can determine the subjects that will receive a label. Every subject in the population can be targeted. The labels are ...
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1answer
13 views

Estimating population mean when using biased sampling?

Say you had a sample of 50 items that was constructed by taking selecting values that were in the top 75% (not in the first quartile), and you had to take 61 items to find those 50 (11 were in the ...
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1answer
76 views

Method for constructing large data set from smaller data set?

Is there a method for creating a large data set from a smaller one? I have a data set of anthropometric variables (e.g. stature, leg length, arm length and so on) So I have 7 variables and 1774 ...
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8 views

Statistics sampling on over-lapping categories

I got a finite population. (e.g. a pool of files) The objective of the audit is to determine whether the files are in order. I need to audit the files for 5 different category on the population. Each ...
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33 views

Rigorous definitions of sample and population

I am trying to understand some basic ideas of econometrics (and mathematical statistics) from the precise, mathematical point of view, avoiding vague explanations. I am beginning to learn about these ...
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22 views

Normalize(Scale) data before sampling or after sampling in binary classification?

I have a binary classification database with imbalance outputs (1 labeled data: 1400 samples, 0 labeled data: 200 samples). I balance data based on a criteria to (200 - 200). Where should I normalize ...
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2answers
92 views

Why do we need confidence intervals?

I am following a video lecture on Statistics, which introduces the concept of confidence intervals in the following way: "A bank vice president is interested in the average checking account balance ...
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18 views

Time-partitions of sample size

I am struggling with explain something I read in a Whitepaper. The essence is as follows. Let's begin with a random variable $X$ defined as number of events in an hours. Further, we assume that $X ...