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

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Population-level data with small n's [on hold]

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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3answers
114 views

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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30 views

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? Thanks! $$ \hat{p} \pm ...
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14 views

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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16 views

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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9 views

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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24 views

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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20 views

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, ...
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1answer
23 views

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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15 views

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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2answers
185 views

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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37 views

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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31 views

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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10 views

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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10 views

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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20 views

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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25 views

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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1answer
21 views

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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1answer
21 views

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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1answer
16 views

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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1answer
30 views

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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26 views

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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1answer
40 views

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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16 views

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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66 views

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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28 views

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 ...
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32 views

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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1answer
31 views

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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10 views

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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1answer
40 views

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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30 views

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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19 views

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 ...
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Determine Number of Users in Control and Treatment Groups

I need to be able to determine how many users should be in a control group and how many users should be in the treatment group. I have read that it is statistically best to split it 50/50, but with my ...
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39 views

Standard Deviation of Averages

Any help would be much appreciated: My data is grouped into 42 categories according to classification of bird catch. Each group contains "X" amount of species, but for ease of input we categorize ...
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54 views

How to assess the probability that a sample belongs to a known population distribution with prior information on block design?

I would like to assess the probability that a sample belongs to a given population, but accounting for prior information of the study design. Short description of the study: I have a large area ...
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12 views

Identify suspect changes within a population

I am looking for a method to identify suspect changes within a population. Let's suppose that I have a database with information on 1 million Chinese companies, including information on the ...
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184 views

Sample size in a population of 300

I have to conduct a survey in the discipline of International relations. I have a list of 300 diplomats to interview for close ended, open ended questionnaire. I want to select randomly every fifth ...
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22 views

Different correlation inside groups with same population

I'm analyzing data from >100 subjects randomly assigned to two groups. Each subject has a skill level and a self-evaluated skill level (the latter being the subject's own perception of the former). ...
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21 views

Removing observations from sample & extrapolation

I have a survey that was administered once to establish baseline, and again to follow up. The baseline was created from a random sample of the population (1,200 respondents). The follow up survey ...
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24 views

Model selection for differences in outcome (binary) across groups?

The problem: A group of agencies (n ~ 20) performance varies significantly on a binary outcome from 0% to 100% (both with small n, more commonly from 20% to 60% for larger n agencies). Is this an ...
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When drawing numbers from a population how to determine if the population shifts over time?

I administer technical interviews for a programming position. During the process I generate a single number 0-12 for each applicant's likelihood to succeed within the company. Over the last year I ...
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Expected rates when scalars that describe populations are not necessarily applied to mutually exclusive members?

So, I was reading a biology textbook, and it talked about how the liver recycles half of its macromolecules a week. It got me thinking really hard about a specific scenario. Assume you have $n$ ...
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15 views

Estimate population parameters base on two-level random sampling

I have a general population(N) and then random-sampled n samples from N. For each individual object in the samples, I random-sampled 1000 activities(for example, let's say 1000 "online display ads") ...
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How much weight should be given to sample mean as an estimate of the population mean?

This R code creates a population of size 10,000 with a population mean of 3 and a population standard deviation of 2: population <- rnorm(10000, 3, 2) We can ...
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58 views

Forecasting - Population Death Rates

Wondering if you can help me out with this problem: I have 2 closed populations of products (call it Product X, and Product Y). Population Size of each product 10 million each (Product X = 10 ...
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59 views

Significance test for subset variation from population

I have customer churn data: independent features like customer gender, location, age etc. outcome feature representing whether he/she has churned or not My population churn rate is around 30% ...