Questions tagged [population]

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

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Population studies - interpreting confidence intervals, should they even be included?

I work with administrative ('routinely collected') data in situations where the data capture the entire population, e.g. hospital records, prison records, etc. When reporting statistics the question ...
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How to sample for compliance when a portion of the population is already known to be non-compliant?

Say I wanted a representative sample to estimate the portion of a population that is compliant on "doing their taxes correctly". Normally, I'd do a random sample of that population to make ...
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Why is standard error of the mean always calculated from the population variance?

The standard error of the mean is often calculated with the formula $\sqrt{\sigma^2 / n}$, which uses population variance (or an estimate of it). However, standard error of the mean is defined as the ...
inquisitive_hamster's user avatar
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8 answers
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Why don’t we calculate the average of an entire given population instead of computing confidence interval to estimate the population mean?

We compute confidence intervals to estimate the true population mean of either a sample (when population standard deviation is unknown) or an entire population (when population standard deviation is ...
Anna Quoc Nguyen's user avatar
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Can spurious correlations exist in the (theoretical) population?

Is it possible that spurious correlations exist between two random variables X and Y in the (theoretical) population (here I mean purely by chance, not due to missing confounders in a model, etc.)?
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Adjust a Sample Mean towards the Population Mean

This feels incredibly basic but I can't seem to find the answer! Let's say I knew the pass rate for an exam in a huge population of students is 50% (let's say millions of students). A new class of N=...
JackWills's user avatar
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Estimating a population total from a stratified simple random sample

I have a stratified population. I want to estimate a population total $T$ from a stratified simple random sample. I have two strategies: I compute $\displaystyle T=\sum_h N_h\bar x_h$ where $x_h$ is ...
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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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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 ...
Steve Fagan's user avatar
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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 ...
Anne's user avatar
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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 ...
Snoke's user avatar
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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 ...
user1995's user avatar
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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 ...
Ale's user avatar
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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 ...
dal's user avatar
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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 ...
Peiran Yu's user avatar
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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 ...
CT1108's user avatar
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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/...
hugh_man's user avatar
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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^...
Galway_bai's user avatar
1 vote
2 answers
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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 ...
Jimolrame's user avatar
2 votes
1 answer
879 views

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 ...
rokamama's user avatar
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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 ...
Peiran Yu's user avatar
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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&...
Marissa's user avatar
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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 ...
madprogramer's user avatar
2 votes
1 answer
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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., ...
Deepak Tatyaji Ahire's user avatar
1 vote
1 answer
335 views

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: ...
myoth myoth's user avatar
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147 views

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 ...
Joey Portier's user avatar
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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 ...
Jacob Bagley's user avatar
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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 ...
stats_noob's user avatar
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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: ...
stats_noob's user avatar
1 vote
2 answers
12k views

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, ...
stats_noob's user avatar
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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. ...
stats_noob's user avatar
2 votes
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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 ...
John's user avatar
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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 ...
Jamal Shah's user avatar
1 vote
1 answer
336 views

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 ...
sb_2006's user avatar
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1 answer
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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 ...
ceno980's user avatar
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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 ...
Julie Kafka's user avatar
1 vote
0 answers
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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 ...
Arnon Weinberg's user avatar
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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" ...
ndevito1's user avatar
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0 answers
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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, ...
Matt's user avatar
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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 ...
Phil Nguyen's user avatar
1 vote
1 answer
360 views

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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1 answer
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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 ...
simran's user avatar
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2 votes
1 answer
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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 ...
Fernando Martinez's user avatar
2 votes
0 answers
21 views

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 ...
civy's user avatar
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1 answer
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Statistical considerations when working with population data

My statistical training has been under the assumption that I will never have access to population level data. In my current role though I do have access to this level of data for a region. Are there ...
Scott White's user avatar
0 votes
1 answer
17 views

Difference inference about x datapoints in sets vs subsets

I have been wondering about a theoretical question regarding statistics. So if I understand it correctly, in the frequentist tradition we want to make inferences from a sample to a population (of ...
Marvinsky's user avatar
2 votes
1 answer
119 views

Normality for population and sample [closed]

I'm new to statistics and got to the point normal distribution. can we define normality for samples too or they're just for population?
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