# Tagged Questions

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

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### Are my regression lines from the same population? [duplicate]

I have two sets of data looking at weight change over time. Subjects within each data sets have weights at multiple time points. The first is a small set of data I used to determine an equation to ...
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### Random Variables, Samples and Population

I am trying to understand the relationship of a Random Variable to a population and random samples. I understand that a Random Variable is a function that maps each event in a sample space to a number....
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### population data normalization

I'm running a prediction model on demographic data, to predict a given feature (e.g. salary range) given age, zip code, gender, job title, ... I have a data set of 50K persons and I reach an accuracy ...
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### Stochastic individual based model

I was going through the article here and can someone please explain what a stochastic individual based model is. Could this be used to model at a population level? Does this model look at each and ...
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### Age-adjustment for differently-defined age bands

I want to produce age-adjusted incidence rates for a disease in a population. I have found the incidence rates by age in one data source, and the total population by age in another source. (The ...
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### Why are we using population symbols ($\sigma^2$, $\mu$, …) instead of sample symbols ($s^2$, $\bar{x}$, …) for Random Variables?

In my Stats course (can't ask prof, it's an online course), we got to random variables and the notation has changed from using $s^2$, $\bar{x}$, etc...to using what we were initially taught are the ...
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### Mathematical models for fertility [closed]

I can't find any papers regarding Dende Kars model for fertility. Can someone please suggest me any paper or book, I should go through to clear this concept?
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### How to compare number of incidents in different geographical areas when they have different population size?

I'm trying to make comparisons between number of incidents that happened in different zip codes. The goal is to figure out whether those incidents happen more frequently in certain areas than others. ...
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### Population models - statistical analysis over time of subpopulation expansion

I am struggling with a statistical method to assess whether two populations have "changed" over time. In my case I have a clonal bacteria species, some strains with a mutation conferring resistance ...
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### How to determine if sampling is representative/similiar to my population

Let say for whatever reason I have obtained a sample of an initial population. (ie. we have paired case:controls on a set of confounders). I wish to compare how representative my sampled (or let me ...
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### What is an example of variation of population?

I needed help with my home work , I am having a lot of trouble with examples for Variation of Population . I have asked everyone in my house , and they don't know . I have also tried the internet but ...
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### Statistical significance testing over population

I have two data sets of 65 data points. I want to test the significance of the difference in distribution between them by Kruskal-Wallis test. But the data sets are not samples, they are the ...
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### Population-level data with small n's [closed]

I have population data (not sample data) and I'm looking at incidence over time in the population. I have small n's (for the incidence and for the overall population). For example, I have an ...
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### Overview of predictive modelling, machine learning, etc.

My text Intuitive Biostatistics is a nonmathematical explanation of conventional statistics. Chapter 3 explains the basic mindset of statistics as analyzing a sample to make inferences from a ...
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### Population Proportion Confidence Interval

Looking at the equations for confidence interval and sample size estimation of population proportion, I don't understand why population size isn't a factor. Can anyone explain? I can't find any ...
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### Trying to calculate industry averages for female employees

I have a dataset that lists employers in a particular industry, the number of employees they have and the breakdown of employees as male or female. I'm trying to get a number that reveals something ...
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### How to determine if sampling is representative to population

Is there any coefficient or some metric that will tell how well sample reflect the population?
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### How to estimate the reliability of an exhaustive list of data?

I have a purported exhaustive list of beneficiaries under a social security scheme. My question is how large must be the sample of this population must be tested to check for fraud etc to derive an ...
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### Is sample standard deviation a valid approximation of population standard deviation for z-scores?

Given a Normal distributions for the population and my sample, a population mean of mu, and a sample standard deviation of s, if I want to find the area under the population curve from x to infinity, ...
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### Comparing a distribution of percentages

I have two populations that I would like to compare, each of which contains N samples. Each sample itself contains many events that can be categorized into 20 different, mutually exclusive, categories....
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### Significance of ratios between study populations

I have 2 published studies I need to compare. Both use the same 2 treatments and measure the same 6 outcomes; however, population size is different between the studies. The hypothesis I'd like to test ...
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### autocorrelation interpretation (annual bird surveys)

I am following a method used by others (McCrimmon et al. 1997 Ecological Applications 7(2):581-592) to look for trends in the annual count of nesting pairs of birds at 29 nest sites over a 42 year ...
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### Statistical methods for data where only a minimum/maximum value is known

Is there a branch of statistics that deals with data for which exact values are not known, but for each individual, we know either a maximum or minimum bound to the value? I suspect that my problem ...
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### Population vs. Sample [duplicate]

Can you use population to refer to a particular population? For example the population of women in Maths Class, from which we can take a sample to measure the height in order to make a judgement of ...
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### What is the difference between standard error and margin of error and when to use which?

Will someone please explain what the difference is between standard error and margin of error and when to use which? I have not had luck finding a simple explanation on the differences anywhere on the ...
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### Difference between errors and residuals. What is the mean and variance of each of them?

Suppose there is a simple linear model $y=\beta_0+\beta_1x+u$. Can we state that $\bar y=\beta_0+\beta_1 \bar x + \bar u$? I have this question because I come up with $Var(\bar u)$ when doing some ...
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### How to sample for success/failure from small populations and probabilities

I am interested in sampling data that comes in a yes/no form. A couple things I would like help in understanding. Why does the reasonable sample size change when my population shrinks? We might be ...
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### Determining sample size given a sample of a sample of a population

I have a collection of data which is composed of 48M records which are a sample of a global real-world population. If I sample 100,000 records from this set of 48M, if I calculated correctly, I have ...
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### Change in variance of a population when a candidate is replaced

I'm working on a population based algorithm. Consider I have a population | 10 | 12 | 18 | 20 | 33 | 19 | 2 | Suppose that the variance of this population is V1. Now I replace one candidate ...
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### Compare two population means at different time point

I am trying to determine the change in the size of a population during a 20 year period using two scenarios. I run the model for each scenario 100 times under different random seeds and then take the ...
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### Method to compare population means

I have two samples from two populations, and I want to test the null hypothesis that the means of these populations are equal vs the alternative that they're not equal. Suppose the populations are ...
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### How to estimate the number of people outdoors in a city?

Currently working on a project about the public facilities' usage in NYC. Now I want to find the relationship between the number of public facilities and the number of people in the corresponding ...
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### Equivalent of significance in population data? [duplicate]

I know that significance tests don't make sense on population data. But how then can I figure out if effect sizes are meaningful? Is it purely a judgement call? Background: I have a census for an ...
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### Sample Representing a Different Population

I have two sets of populations: containing 1.5 million and 5.5 million units. I need to select a sample out of 5.5 million population so that the sample represents the 1.5 million population based on ...
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### Estimating variance or coefficient of variation for population given total and count for four segments of population

My goal is to estimate the coefficient of variation for a population, but the data we have been given is very limited. All we have is the total and count for four segments of the population. The ...
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### Do I have to test normality for both groups when comparing from a single population?

This should be an easy one. I'm a novice when it comes to statistics and English isn't my first language so bear with me. I have one population that numbers about 700. Of these 700, 25 are of special ...
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### Understanding sample and population (real life scenario)

A real life case: a firm desing, produces and sells 52 vehicles. I collect failure data of the components of the vehicles. after a time, -for example- for the oil filter I have 52 data. Some of them ...
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### Uses and estimation of Student-t distribution

My question relates to a confusion between how the Student-t distribution is often documented versus how it is used. In the documentation the Student-t is used (from Wikipedia): when estimating ...
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### help me choose statistical analysis for my undergrad thesis [closed]

firstly, i'm sorry if i'm not very good in statistics, i just need to finish my undergraduate thesis, but my professor is very busy, that he always don't have time for me to consult my research. so ...
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### Skewed population example

"Consider a strongly skewed population (e.g., waiting times at airport security screening)." My book always uses that example when referring to skewed populations. I don't understand why would that ...
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### Population vs sample

When we think of linear regression, the implicit assumption is that we only observe a small fraction of a possibly infinite large population. Thinking of simple averages, imagine a fair die. The ...
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### Estimating actual score from small sample when population known

My inclination here is that there's no statistically sounds way of doing this, but I want to verify this. Suppose you have a population P, and you are measuring test scores across the population such ...
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### Sample similar to Population

I have 100,000 customers, each customer has a few variables associated with them, separated into 100 groups. I want to find a sample of 10 groups that best represents the entire 100 groups. What are ...
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### Statistical Data Changing Over Time

I am attempting to determine voter registration rates by race within specific precincts in my county. The local Supervisor of Elections' Office provides data online of the voter registration rates by ...
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### What can be inferred from Simple Random Sampling?

Suppose I have access to a population data set. I then perform Simple Random Sampling on this data set to pull a sample. I perform some tests to see if the population data set and the sample data set ...
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### Homework: Population mean inference with unknown standard deviation

I am doing my homework on population mean inference with unknown standard deviation, and I hope I could use your help with this one particular problem: During one week in January, OfficeMax ...
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### Sample size for entire population to determine sub population?

Let's say a bus company has 500 markets with an average of 10000 passengers each day but some markets as large as 100000 and some as small as 300. How would I determine the simple random sample size ...
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### Assessing effect of sample in its population

I have population of 200 people with their BMI . I want to remove 30 people of similar characteristics from the group and see if that makes any statistical difference on BMI of population(now 170). I ...