Questions tagged [sample]

A sample is a subset of a population. Statistics, in general, is concerned with using samples to make inference about the parameters governing a larger (possibly infinite) population.

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7 views

Probability vs Nonprobability Sample [on hold]

I've read a classification of samples (probability and non-probability samples) but in need of more examples. Suppose this year a company is going to conduct a customer satisfaction level survey on ...
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Why are these statistics used to find out the sample variance's distribution

It's pretty much what the title says, I'm using Canavos' Applied Probability and Statistical Methods to refresh what i know about the sample distributions. I'm now looking at how the sample variance's ...
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Different sample size of control and test groups

Hope someone can help my question: I have a survey study with one control group and one test group. Each is set to have 500 completes. However, we are short in sample in one group: Test is 350 and ...
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38 views

Infering population from a sample?

I took a test in class and found it to be difficult. So I asked in my WhatsApp group if others felt the same. 4/36 people replied yes they felt it difficult. Others did not respond either in yes or no....
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17 views

How to calculate the Margin of Error in this specific scenario?

Assuming I have a population made of hotel bookings for a specific period and I need to send a survey questionnaire to each guest (guest=booking) by email. To simplify things, let us assume the ...
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18 views

Confidence Interval for the Difference Between Proportions in complex samples

I have two complex samples (with different sizes) from the same population in different times. I used the survey package to create designs for them: ...
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Calculate a Conditional Expectation via Samples

Consider a binary random variable $Y \sim p(Y)$, a random variable $X \sim p(X)$ (can be discrete or continuous) and a conditional distribution $p(X|Y)$. Suppose that I generate $N$ samples from $p(Y)$...
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intuition behind SD+

so i was reading statistics by Freedman and in the section where he describes the t-test he goes on to explain why we would use the SD+ instead of the regular SD to calculate the S.E with the sample ...
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28 views

How do I sample N items from a list ensuring the samples are as similar as possible to each other?

Is there anyway to sample 6 numbers without replacement this list of 12 numbers ...
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37 views

2x3 design, binary out come sample size calculation?

I'm designing an experiment as part of a marketing assignment. I'm planning on running a 2*3 between-subjects design (6 conditions comprised of two factors, one with 2 levels and one with 3 levels). ...
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38 views

How can we write the sample variance's formal definition of a continuous random variable considering Bessel's correction? [closed]

I am trying to find the formal way of writing the sample variance of a continuous random variable considering Bessel's correction. I ask because the sample variance is usually written this way: $$ ...
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When to use a certain sampling technique

I'm taking a class where we learn about different sampling techniques. For the most part it has come down to SRS, Ratio/Regression/Difference estimation, Stratified random sampling, Systematic ...
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Smaller dataset or bigger but risking ovb?

I am testing whether financial access is correlated with the education of young individuals using a longitudinal panel. Among the controls I am using there is parents' education that is a determinant ...
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Does reliability of measurement affect the minimal sample size required?

The following calculator (like many of its kind) uses a number of variables to determine an adequate (and importantly, representative) sample size: https://www.calculator.net/sample-size-calculator....
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26 views

Sample size prediction in multivariate A-B testing

I need to run an A-B testing with one control group (40%) and 3 variants (20%) each. Base line = 0.65 Target lift = 0.25 Power =0.8 Confidence = 95% I found following R code to find minimum ...
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Test whether multiple (>2) sets of samples should be combined into one set

I have a set of problem instances of some type, and a set of algorithms which all solve that type of problem. The problems come in m different sizes and for each size I have the same number of ...
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How does the nth sample impact Mean and Variance? [duplicate]

Given the Mean and Variance of $n$ samples $x_i$: $$M_n=\frac {1}{n}\sum_{1}^{n} x_i$$ $$V_n=\frac {1}{n}\sum_{1}^{n}(x_i-μ_n)^2$$ How do Mean and Variance change, when we take into account one ...
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Calculating change in mean and standard deviation of Sample X due to replacing p% of X with data from another distribution

Suppose we have two independent normal distributions $A \sim \mathcal{N}(\mu_a, {\sigma_a}^2)$ and $B \sim \mathcal{N}(\mu_b, {\sigma_b}^2)$. Suppose that we have a sample $X$, which is drawn from $A$...
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Dealing with self-selection in the treatment group

I wanted to do a Randomized Controlled Trial for a new curriculum that was announced in my area. The issue is, certain teachers, under the organisation that I'm working with, have selected to teach ...
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Weighting Survey data - Achieved sample, Survey sample, population

I have designed a small survey for my work place of 2000 people. 200 people were selected based on gender (Male female), age group (4 25-year age groups) and working grade (a,b,c). Out of my sample ...
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Find number of elements to check for finding false negative rate

I have 3500 pictures that were classified in four different possibilities of match: very low (16%), low (1%), high (30%), very high (53%) All labels are not known, i.e., I don't know if they were ...
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Multiple linear regression: am I interpreting the methodology right?

This is a follow-up question to 1 and 2. So we have the normal linear model \begin{align*} \textbf{Y} = \textbf{X}\beta + \epsilon \end{align*} where $\epsilon\sim\mathcal{N}(\textbf{0},\sigma^{2}\...
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What exactly is the sample size of an investigation?

My understanding of sample size is that it is a portion of the population that serves to represent the population. However, I'm not sure if the sample size of an investigation to investigate how X ...
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What is the sample size formula which i could possibly get minimum value in-vivo studies?

I am an undergraduate students who is struggling on how to do in vivo studies with my low budget. Therefore, I ask some help of you just in case you know about what sample size formula that I could ...
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How to infer the distribution of a statistic (Bayesian inference?)

I have a list of approximately 30,000 venues in a major US city. These venues hold all kinds of events, sports, conferences, concerts etc. I want to know the distribution of the 'capacity' of these ...
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Estimate frequency based on given sample

I have a list of users (~25 million) and a dataset containing events created by the users in a specific time window (eg all tweets of all Twitter users that happened in a month - on avg I have 100K ...
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Using mean length and mean weight to calculate mean BMI?

Is it valid to use mean length ($h$) and mean weight ($w$)) from a given population to calculate mean Body Mass Index ($BMI = \frac{w}{h^2}$) for that population?
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A question about power for a cohort study

In short, we are planing a cohort study, were we want to investigate the occurrence and the importance of a given event on response of a treatment. We expect the event to occur in about 2% of all the ...
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25 views

Is there any way to resample in order to change the distribution of a sample?

I ran an experiment that involved an independent variable which is known to have a right skewed distribution. However, in the experiment, the independent variable was distributed differently between ...
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343 views

How to figure out whether the data is sample data or population data apart from the client's information?

What are the ways available to figure out whether the data is sample data or population data apart from the client's information?
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47 views

Calculating required sample size for estimate lower bound on 95% of the population

I'm interested into sampling from a population, with a long time to get a sample (O(1), usually 1/2 mins), with lots of candidate populations to sample from (running a metaheuristic optimization). I ...
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18 views

Testing whether two timeseries samples are from the same population

I would like to test if different timeseries samples (over the same period of time) are plausibly from the same population. e.g. popularity of movie Avengers over time from different websites. The ...
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165 views

Calculating a sample size based on the target width of a confidence interval with stratification

I am reviewing a sampling design devised by a colleague and completely fail to understand it, although I am not a novice in statistics (but not a huge expert either). The said colleague is no longer ...
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28 views

Sample from a distribution constructed by Dirac measures

I am reading the paper in the following link https://link.springer.com/article/10.1007/s11203-009-9037-8 In the page 19, the author suggests to sample $\eta_i$ from the following distribution $P^{\...
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Unbiased Estimator of the Standard Deviation of the Sample Standard Deviation

I'm looking for an unbiased estimator of the standard deviation $\text{SD}(s)$ of the sample standard deviation $s = \sqrt{\frac{1}{n-1} \sum_{i=1}^{n} (x_i - \overline{x})^2}$. I have found this ...
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A question about the definition of sample

Let $(\Omega,\Sigma,\mu)$ be a measure space. The definition of a sample is that it is a sequence of iid random variables $X_1,\ldots,X_n$. Usually random variables are real valued and the ...
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33 views

How exactly can I get sampling distribution of means for calculation of standard error?

Let's denote population by $ N $ and sample with which I want to make inference about $ N $ denote by $ n $. Let's assume I have already collected $ n $. Now I want to get means for sampling ...
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33 views

Probability density of the product of independent identically distributed random variables

Let $X_1, X_2, \dots , X_n$ be a random sample from the PDF $$f(x;\theta)=\theta x^{\theta -1},\;\; 0<x<1,\;\; \theta > 0$$ What is the probabilty that $\prod_{i=1}^n X_i > t$? The joint ...
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Standard error of sample variance

We know that an unbiased estimator of the variance is: $$ \hat{\sigma}^2_{unbiased} = \frac{1}{n-1}\sum_{i=1}^n (x_i - \bar{x})^2$$ I was wondering, does it have the smallest possible standard error? ...
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Sample is almost the same as the population

I'm interested in a situation where I have a small list of events, somewhere in the range ten to a few hundred. Each event can be a 1 or 0 outcome. I have a good reason to believe that the factors ...
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1answer
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What distance function to use for matching observations on a mix of ordinal, nominal and numeric variables?

I'm trying to match potential respondents to a random sample from the target population, and not sure whether any of the usual methods available out-of-the-box in e.g. R are right for the job. ...
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Problem on conducting a hypothesis test with sample data

I'm trying to perform a statistical tests for the sample data(n=63) which is the effect of smoking for time(measured in minute) to fall asleep. First, I set a null hypothesis, there's no effect of ...
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Hypergeometric Probability with a twist

A manufacture receives a lot of 200 parts from vendor. The lot will be unacceptable : If more than five (>5) parts are defective. The manufacturer will select randomly K parts from the lot ...
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Sample size (CI 95%)

I have two groups (treatment and placebo) and for each group I have the 95% CI mean calculated as per here. I want to do the same for calculating the 95% sample size as per table 11 of this paper: ...
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20 views

How to decide sample size for validation?

I have data having over 20000 rows. 1) I am going to use a tool to test how many error rates this tool will calculate in this data. 2) And then, I will randomly choose some data and check how many ...
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Favorite sequence in 10 flip tosses

I have the following question. Somebody likes to flip coins. In particular, this person is delighted to get a sequence HTTH. Assuming the person flipped coins 10 times, what is the probability that ...
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Minimum Sample Size for M&A Event Study

as statistics beginner I was hoping you could help me with regards to the following problem: I wanna conduct an event study (analysing abnormal returns of share prices) to derive performance effects ...
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What does the distribution of samples from an MCMC method converge to without repeated samples?

Suppose I have an absolutely continuous distribution with density $f(x)$ and I use an mcmc sampler which has accept/reject step to sample from this distribution. In the final samples, there are some ...
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Conditional Probability Based on Sample When Population is Known

I have a count from each U.S. state of people that ride bikes. I want to know whether the count is larger or smaller than expected relevant to the population of each state (I also have the population ...
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75 views

Deciding on population vs. sample

I have been researching when to classify a dataset as population vs. sample for many hours now for a statistics project I am doing. I have a dataset of NFL combine data and one thing I need to clarify ...