Questions tagged [population]
A population is the entire set of units from which a sample may be drawn.
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compare distribution a categorical variable between a population and a subpopulation
So I have the following situation of having a population P with individuals belonging to categorical variable A, ..., N. From this known population I created several sub-population P1, P2 (each time ...
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13 views
Sampling theory of correlation; sign of population correlation coefficient & hypothesis design
I'm currently studying 'Estimation of population correlation coefficient from sample correlation coefficient.
Source: https://newonlinecourses.science.psu.edu/stat501/node/259/
Test statistic is like ...
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2answers
104 views
Calculating the variance of sample, knowing the mean of population
Suppose that I somehow know the mean of the population. And I want to calculate the variance of a sample.
Should I subtract population mean or sample mean?
Is there any situation in which I should use ...
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14 views
Range of population variance [duplicate]
I have a set of numbers between 0 and 1, for instance, {0.4, 0.1, 0.0, 0.8}. What are the minimum and maximum values of population variance on such set?
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1answer
31 views
Population Mean Estimation using Poisson Regression?
Assuming I have count data, where x is the counted variable of interest and y is some total number of counts for a given sample. Then, can I improve my estimate of $\mu_x$ by using a Poisson ...
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38 views
Issue when deriving an expression for normal distribution population parameter PDF given measured sample parameters
So I came across an issue when I derive the equation of the joint PDF for the population mean and variance based on measured sample mean $\bar{x}$ and sample variance $s^2$ and I am not quite sure ...
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66 views
Is my Correlation reasoning correct?
I am trying to understand how to arrive at $r = \dfrac{Cov(X,Y)}{\sigma_X\sigma_Y}$ with a logical narrative. This in fact is kind of continuation from my this unanswered question.
I see that by ...
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34 views
Time series: sample vs. population, population vs. realizations of random process
Suppose we have 120 monthly observations (Jan 2000 - Dec 2009) of unemployment rate and suppose we would like to use these in order understand the unknown underlying stochastic process that generated ...
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2answers
128 views
How do I compare means when I have a sample and the whole population?
I have the following didactical exercise to carry out:
Scenario
I have the avg room price for all the hotels of my chain (32 observations of the 32 hotels). Then I have the avg room price for a ...
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2answers
34 views
Testing that training and test data sets (not vectors) have been drawn from the same population in R
I have two data frames in R (training + test). The test set is not drawm splitted from one sample by myself but I got those two dataset and am supposed to built the model on the training set and make ...
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1answer
53 views
Two-sample T-test
Hi I conducted the research where I measured germination of seeds in different ecological conditions. Each seed sample (one germination data) was exposed to different combination of ecological ...
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24 views
Likelihood that two random sample sets come from the same population
I have two random sample sets of 100 points, with 7 possible answers (A – G) each. The sets are as follows:
Set 1
A 49
B 22
C 14
D 7
E 4
F 4
G 0
Set 2
...
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21 views
How to calculate whether a disease outcome in a population is by chance or significant?
I have a huge dataset of longitudinal medical records. Each record contains indications for drug and disease.
I have been able to calculate the Outcome Rate in the population given a particular drug....
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15 views
How to test the difference in mean between a group and a sub-sample of the group?
A year ago some of my colleagues made a rapport for a client in which they were to report the mean of approximately 100 students examination grades. Here a year after the client has found the ...
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2answers
124 views
About Sampling and Random Variables
So I've recently started an introductory course in econometrics and I'm having trouble grasping the idea of Random Variables and Sample distributions
If we have a population and we take a sample $Y= \...
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0answers
20 views
Comparing averages of unequal population sizes
Imagine the following problem: I have 1000 plots of land. On each plot of land I plant 1000 Oak trees and 1 Elm tree. Each plot of land differs in multiple parameters (e.g. sunlight, soil type, ...
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45 views
Comparing sample correlation coefficient with population correlation coefficient
Assume there is a population, P, of size N. Each member of the population has three variables associated with it, a nominal variable C (with m unique categories), and two continuous variables X and Y....
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1answer
27 views
How to find a population of healthy products among many samples
A measurement is performed on 100 equal products. Some of these products contain defects. I expect defects to be present on a small number of products, say a total of 10. Now I want to create a ...
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19 views
Update to estimate of population mean based upon new sample
Suppose I sample some phenomenon with a potentially moving mean, let's say height of males on their 18th birthday, and I run this survey every year. Each year I produce a sample mean of height, which ...
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14 views
Confidence intervals interpretation in whole population studies. Can they represent replication variability?
I got the surgery time of each surgery ward patient. I want to compare the mean surgery time of each ward using a series of regressions in which the independent variable is being or not in a specific ...
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0answers
14 views
Percentage of Middle Class People Between 15 - 29 years old, using two different percentages
I'm trying to calculate the percentage of middle class people between 15 and 29 years old. I know that 27.9% of the total population is inside that age period, and also that 15% of the total ...
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39 views
Appropriately comparing subset to entire population
I am currently running a few analyses in which I want to compare a subset of my sample data to the entire dataset. More specific: I want to find out whether respondents who live in a certain ...
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1answer
43 views
Is this conclusion drawn from sample or population?
"When asked what they would use if they were marooned on an island with only one choice for a pain reliever, more doctors chose A than B, C or D."
Is this conclusion drawn from population or a sample?...
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10 views
Population Stability Index: Why ln not log? [duplicate]
The Population stability index is based on natural logarithm.
http://ucanalytics.com/blogs/population-stability-index-psi-banking-case-study/
The formula looks somewhat similar to what I have seen ...
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0answers
35 views
Interpreting PCA, comparing genetic structure within mice population from two continents
I'm interested in comparing the intra-regional genetic relatedness between two populations of mice. One population is native to Europe, while the other is native to North America.
I ran PCA to find ...
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1answer
36 views
Counting Number of People in Building Given Entry/Exit Data
I've been asked to analyse entry/exit data for an office to find out the minimum number of people present in the building for fire safety reasons. The building operates 24/7 so there should always be ...
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1answer
32 views
Simulating samples from a population based on marginals
In Germany's health care system, health care expenses $Y_i$ of individual $i$ in a given year are explained by $K$ dichotomous risk factors $(X_{1i},\dots, X_{Ki})' \in \{0,1\}^K$. The multiple linear ...
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1answer
32 views
How to find mean and variance of population of flat probabilistic distribution
I'm trying to understand the difference sample variance and population variance and how former converges to latter after ...
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18 views
Quantifying similarity of two objects in a population on certain characteristics
I have a set of objects (these are businesses) and for these businesses I have data on a number of characteristics. To keep this simple, we will consider these to be
number of staff
number of ...
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19 views
Comparing population averages while accounting for changes in composition
I have two populations (i.e., men / women) with different average measurements (let's say height). I observe the combined average of their height decreases. I also observe the proportion of women ...
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19 views
Statistical Control vs. Sample Representativeness
Assume I have a sample that is NOT representative of the population.
To illustrate an example, assume I the dependent variable called Violations that measures the number of job violations, and I ...
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0answers
14 views
Age-adjusted rate across many years
I have incidence-level data for heart disease that includes patient age and region. I calculated disease counts by region and now I want to calculate an age-adjusted rate for each region.
The data ...
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0answers
10 views
Multi-tiered (nested?) uncertainty & confidence bands - subset populations
I have a current and historical dataset of likelihood that a population gets into a car accident. I have my predictions for a rare event - say the % chance that a given driver gets in a car accident ...
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36 views
Can populations of different sizes be compared sensibly?
I am new here but have a question about population comparisons.
I am trying counting pollen grains using an Scanning Electronic Microscope (SEM). I want to compare the abundance of a certain type ...
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1answer
30 views
Why does a sample of n of a population of n retain degrees of freedom of n?
I understand that if you take a sample from the population that a single data point cannot freely vary if $\bar{x}$ is known and you have the remaining sample items. However, I do not understand why "...
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26 views
How to analyze size frequency data from over 70 sites
When I started my PhD, I had virtually no prep-time. My advisor needed me in the field and told me to go grab samples. As such, my planning wasn't the best, so sorry if this is a completely terrible ...
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1answer
123 views
Getting the probability of a sample being between two values
I am learning on probabilities in populations and samples now but I'm stuck on this question.
Suppose we have a sample with n=35 of a population with a mean of 80
and standard deviation of 5.
...
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0answers
36 views
Identify the underlying distribution from multiple samples
I have $30$ unequal samples ($n_i >1000$) from a supposedly same population. How should I go about identifying the underlying distribution of the population using these $30$ samples simultaneously?
...
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1answer
26 views
Sampling error size vs population size
Reading a methodology for reporting plant/seedling survival I found the following statement:
In small plantations or very small strata (1 to 3 hectares) the sampling
error size is usually high ...
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26 views
Law of “large but not infinite” numbers?
Say there is a population of size $N$, e.g. the population of human beings in China. The distribution of a given characteristic of these individuals, e.g. height, follows a distribution $X$, with mean ...
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57 views
How to calculate population weighted yearly average temperature for gridded estimated climate data?
I don't have a statistics background, so let me go straight with my question. I need to calculate population weighted yearly average temperature for gridded ...
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0answers
29 views
cluster sampling: how to select a representative cluster of wider population
I have a population census dataset of a large city with around 80 categorical variables which have been summarised at the level of an enumeration area i.e. % of households that own their property; % ...
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1answer
33 views
Gini coefficients - Accounting for firm exits
What is the appropriate way to measure the Gini coefficient over time in an industry where a large number of firms are exiting? Should the Gini coefficient be calculated using the initial number of ...
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1answer
365 views
How to check if a sample is representative of a population, across several criteria.
I have a total population of several hundred houses, which have different sizes, prices, and ages.
I want to be able to select a random sample, of a few dozen or so houses, and test how ...
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0answers
28 views
Using randomisation tests for population data - question on time dependence and effect size
I have been using randomization tests on population (as opposed to sample) data and would like to double check that my methodology is correct and get advice on how to expand my analysis.
Some ...
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1answer
12 views
How to reduce sample data to a smaller scale?
In statistics let's say for a specific city (call it "City A") 1000 people die of driving related accidents annually. The city has a population of 2.7 million people. In another city, "City B" 3000 ...
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1answer
48 views
Why does the sample size not change much for large populations?
Afternoon,
I have a number of different large data capture processes with populations from 100,000 up to 4.5million forms.
I am wanting to determine the error rate in the capture process so am going ...
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0answers
17 views
Correcting popularity for population
If I have a list of products with votes (no restrictions on number cast for each object), I want to estimate popularity correcting each product by the number sold. What's the best way to tackle that? ...
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18 views
Intuition for effect of population size on quality of sample mean as an estimator of population mean
I would like to compute the mean $M$ of subsystem entropies $H(x)$ for a physical system $X$ with $2n$ particles and subsystems $x$ with $n$ particles:
$M(X)=\sum_{x\subset X}H(x)\,.$
The number of ...
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1answer
40 views
Hypothesis testing on two proportions in two finite populations
I have data collected over two years where:
Year 1 = 34 successes in the representative sample of 49 taken from the finite population of 122, and
Year 2 = 45 successes in the representative sample of ...
