Questions tagged [population]

A population is the entire set of units from which a sample may be drawn.

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question of a Poisson random effect model

Assume a Poisson random effect model (with a random intercept) $$\log E(Y_{it}|b_i,x_i)=\beta_0+\beta_1x_i+b_i$$ $$b_i \sim N(0,\tau^2)$$ How to derive the population-averaged effect of one unit ...
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When I have population data do I need probability and can I infere? [duplicate]

Say I have data about a population and I want to analyze them, then in my understanding the "sample" is the population. And then do I need probability, like p-values, confident intervalls ...
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Measuring variability of log in hours

I'm working on measuring the usage patterns of an app for a population of users. I want to find out if they usually log in at the same hours or if their usage times vary a lot. The variance of the ...
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Combining results of 2 survey sources

In my study, I have data from 2 survey sources (from 2 groups of people). They are very different from each others. A few major differences: First group did not get paid to answer the survey while ...
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Another question on population vs. sample

The problem that bugs me can be boiled down to: "What is population? (Really)." This is my thought experiment I've dealing with for a few days. There is a researcher A, who gathers data from ...
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How to compare trend of two different datasets?

I have two different datasets (ID 1 and 2) which show the number of animals per hectare for each year. I need to know if the trend for the first periode is different then the trend for the second ...
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Analysing PSI for much smaller sample size

I would like to analyse if data of my customers have changed recently, hence wanna check Population Stability Index. However, number of my customers have decreased recently, hence number of samples ...
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Sample Bias in Study

I have following Study statement: A council wishes to study the digital awareness of its resident senior population (over 65 years), so it questioned in person 50 residents randomly chosen from a ...
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What actually is Population of Data?

I have just started my statistics journey and as part of assignment I was given one statement and had to deduce population, sample etc from it. The statement is as follows: A council wishes to study ...
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Effect size calculation?

We are currently analyzing medical records data. During the study period, we have a minimum of 60,000 population patients in group ...
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Does it make sense to have error bars if there is no uncertainty in calculating the percentage?

I know a couple questions have been asked on this site that are similar, but they were slightly different from mine, and the answers don't seem to apply to me directly. I have the following simple ...
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What sort of statistical test should I use to determine significance between independent groups in my (kind of unprecedented and strange) study?

I have designed a study where I am collecting price data from a particular niche of businesses in my state. Some of these businesses are owned by a conglomerate, and others are not. I want to know ...
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Do I know the population or just a sample?

I have to analyze an artifact (a pencil), more specifically I need to analyze the production of the last semester of 2021 (during 2022 the artifact is still being produced but in my analysis I'm not ...
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non-parametric inference assumption

This may be somewhat of a philosophical or foundational question. In parametric inference, we make a distribution assumption to relate sample to population. Even in a non-parametric technique such ...
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What's population, what's sample, in a website conversion hypothesis test?

Context I am a marketer; and I run marketing campaigns and website design tests a lot. There are many tools - such as online A/B testing calculators - out there to help me test the statistical ...
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Sample size of population to be representative of all names

Im not a mathematician but need some help trying to calculate the sample size of a population needed to be indicative of the whole population with respect to the prevalence of names. Assuming sample ...
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Can I use an I-MR chart for a process in which the sampling time is random, or not regular?

I am currently studying a process which produces one sample for testing at one time. Not only that, the time at which the sample is taken for inspection is also not fixed but it varies. The process ...
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Comparing capture efficiencies of sampling gear?

I have capture data for a fisheries population assessment. Two different crews were used that did surveys separately, each with variations in specifications of the gear that they used (same gear type/...
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When calculating Horwitz-Thompson estimator, is it correct to multiply the pairwise terms of the calculation by two?

I'm currently trying to learn how to calculate the Horwitz - Thompson estimator for population variances. Using this formula $$ \hat{V}ar(\hat{\tau}_\pi)=\sum\limits_{i=1}^v \left( \dfrac{1-\pi_i}{\pi^...
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Representation of population data mean/median (similar to BMI/age curve)

I want to represent my data (n=150 samples with a curve of value over time, similar to BMI representations in figure). Possibilities are either mean/std and median/percentiles. The question are: Can ...
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Can the sample equal the population?

I came across this test question from an introductory statistics course for undergraduates in biology. The solutions are in square brackets. Which cases are possible? The sample is larger than the ...
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How to confirm population distribution type in industries

Studying some basic distribution problems that always start with "assuming this or that is a normal/exponential distribution", got me curious - how do people even arrive at these assumptions ...
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Is it appropriate to put "error bars" on data when you have the full population?

I have data on the large number of people who were applying to receive an award. Everyone who applied must fill out a survey and specify their gender (although they can choose "prefer not to say&...
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Which test to use when I have population data?

Population Data I have a large dataset of government funds to all the training schools in London. It's a complete dataset i.e. it represents the population I am studying. I only want to know about the ...
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Fitting a von Mises Distribution over the Global Population

For a statistics course I'm taking this semester, we decided to conduct a worldwide survey. One of our questions, is an approximate coordinate of where the respondent lives. Our instructor recently ...
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Why is the expected value of any data point in the sample equal to population mean?

Suppose we have a distribution of heights of all males in a country. Let population size = N. Now, I take a sample of 100 males = {h1,h2,h3,....h100} How is the expected value of any data point, i.e., ...
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Problem with weigts in survey analysis of GSS cross-sectional data

I have a dataset made from https://gss.norc.org/get-the-data There is a description from the codebook how to use weights: ...
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Method for calculating number of employees

I need to calculate the number of employees in a given number of organisations. I know how many organisations there are in total and I know the number of employees in 50% of those organisations. Some ...
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How to interpret big data models with poor local prediction

Dear big data experts, I’ve been confused with how to think about machine learning models trained through population-level big data that could not make good predictions at the individual level. I ...
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Computing BIC and other methods to find most likely K cluster

I have recently been diving into the world of population genetics and still remain with some questions when trying to conclude what the most likely value of K for my dataset would be. To give you some ...
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Given a population of values which each have unique uncertainties, how do I determine the mean and standard deviation of the population?

I'm trying to determine if a material has a different spectroscopic response under different conditions. In short, I measure 100 points on the sample, and the data output at each point is a data ...
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Calculating Sample Size For Multiple Groups (in R)

I am working with the R programming language. Suppose I have 1000 patients in a medical study, and I want to take measurements on these 1000 patients. 500 patients in Group A 250 patients in Group B ...
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Estimating the Population Mean with the Sample Mean

I am trying to better understand how the sample mean can be used to estimate the population mean. Using the R language, suppose I have the following population: ...
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Sample Size Determination When Population is Unknown

I was looking at the following formula for determining the sample size: Here are what the following terms in the equation stand for: This equation looks straightforward - if the population size, ...
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Are inferences made on a set of samples (from the population) ONLY intended to describe that set of samples?

Are inferences made on a set of samples (from the population) ONLY intended to describe that set of samples? Suppose you have measurements on the height of 1000 giraffes from zoos across the world. ...
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What can we infer from the sample size and mean?

I came across this interesting question today and haven't been able to understand how the statistician was able to arrive at the estimate: A sample of 300 customers were asked to participate in a ...
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How to interpret 'e' in Yamane's Formula?

If I use e=0.05, and from Yamane's formula I obtain, say, a sample size of 300 from given population size. Now, for instance, I obtain some descriptive statistics from the sample size such as the mean ...
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two proportion z test with large population

I want to test for differences between two proportions, specifically, a complete count of the number of events occurring within a population in year 1 vs that in year 2. I thought a two proportion z ...
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Why do 95% confidence intervals contain the unknown population mean 95% of the time?

I am learning about the Central Limit Theorem (CLT) and confidence intervals from this online course. I have learnt that that the CLT states that the theoretical sampling distribution of a sample ...
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When we up-sample the training set, don't we introduce selection bias?

When doing supervised machine learning in the health or medical domains, we often have a target class that is relatively rare (e.g., prevalence 1-10% of cases). There are a few techniques we can do to ...
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How to study data variance with significant and non-significant regression response?

Background My research field is within development of Finite Element Human Body Models (FE-HBMs) with the aim of including geometrical population variance (3D shape). My background is not in ...
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Practical use for heritability value at sub-population level?

For me as a layperson, heritability is something that much smarter people than me calculate, and there are several questions already on the forum about how to do that (eg, this and this). I ...
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Stratified Sampling from a population according to given weights

I have a population and i want to take a sample from it in order to examine a mean of a characteristic (say $p$ the probability of having an infringment).My population is 13996 and are divided into 7 ...
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How can you compare changes in a shifting population over time?

How can you compare changes in shifting population over time? For instance, say I have the proportion of retired people in a town at time 1 (T1), then again at time 2 (T2). The "population" ...
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Central Limit Theorem: Is the likelihood of obtaining some sample mean exact when n is not infinity?

The central limit theorem states: $$ \lim _{n\to \infty}{\sqrt{n}}{\left({\frac {{\bar {X}}_{n}-\mu }{\sigma }}\right)} \sim \mathcal{N}(0,1) $$ Which means if I ran an infinite number of experiments, ...
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What do "random sample" and "particular population" mean in clustering?

Yesterday, from a suggestion of @Dimitriy V. Masterov here, I saw from the given link about one of the reason we can avoid clustering is You want to say something about the association between ...
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Why a variance of a sample mean is the population variance divided by a sample size?

On the wikipedia page about variance I have found the following equality $$ Var(\overline{X})=Var(\frac{1}{n}\sum_{i=1}^{n}X_{i})=\frac{1}{n^{2}}\sum_{i=1}^{n}Var(X_{i})=\frac{1}{n^{2}}n\sigma^{2}=\...
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Population growth projection

Que ) Population grows in such a manner that [1/P(t) ] dP(t)/dt is a linear function of log P(t) where P(t) is the population size at time t . Obtain the explicit expression for P(t)* In this question ...
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How do you know from what population a sample comes?

My question is say you take a sample say of people weight and you get in pounds right [100,220,230,240] many people say this sample come from a normal distribution population. But my question is from ...
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What's the population inclusion criterion in an unpaired two-sample t-test?

I'm conducting a clinical trial in London, UK on 200 women suffering from breast cancer and would like to investigate the difference in a biomarker's concentration (continuous variable) among two ...
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