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

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Confirm heterogeneity in a fish population over time

For my thesis I have to statistically prove that heterogeneity is establishing over time, more specific in the weights of a fish population. My dataset consists out of the weights of 17fish and the ...
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66 views

Standard error of a population

I measure the weight of 100 people and pick 20 lots of 5 people from these 100. Therefore n = 5, repeated 20 times. The 100 people represent the population and groups of 5 people represent samples ...
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1answer
16 views

Are daily updated data a sample or a population?

I want to do some tests based on all historical data of a product updated on a daily basis. These data are not supposed to have any time trend associated with them just be pulled on different days. I ...
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44 views

Standard Deviation of small population (less than 30)

Do we calculate the Standard Deviation of a population the same no matter how small (say less than 30) population size gets? Does distribution type play any roles in this? Thank you in advance
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1answer
35 views

Chi-square test on a sample from population having an unequal distribution

I got a sample with an unequal gender distribution ($30$ males to $200$ female). This distribution is quite "representative" for the population the sample is taken from. Nevertheless, in a paper, ...
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172 views

How can you tell if a yearly increase in population is statistically significant?

I have daily data for two years consisting of "number of sightings" each day. Is there a way for me to test whether the data for year 2 is "significantly" higher than the first year? I know the ...
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14 views

Testing if two population means are equal

In the situation where I have two estimated population means, and I want to see if they are equal, I compute $\frac{ \bar{y_1} - \bar{y_2} }{ se(\bar{y_1} - \bar{y_2}) }$ and compare to the ...
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27 views

Reducing the amount of data by extracting a representative sample of my population

I have 6 B&W images representing different wavelengths (i.e. Landsat bands) of the Alta Valtellina (Italy). I extracted from the images only the areas of bare soil. Now, I want to perform a PCA on ...
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34 views

How to determine an appropriate sample size for a normal distributed population?

I am trying to extract a sample from a given population. Assuming the population distribution is normal (I still have to test it, but I am confident it is), since the number of observations in the ...
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23 views

Compare variable in two independent samples

There is a hypothesis that in online health communities influential members (higher reputation) tend to post more emotional support than regular members. Emotionality of answers were determined by a ...
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32 views

sample versus population in experimental data

I am not statistically oriented, so I am hoping you might be able to help. I have a small lab setup that mimics a larger natural process (natural disaster). I have designed and completed 46 ...
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113 views

Male and Female Chess Players - Expected Discrepancies at Tails of Distributions

I'm interested in the findings of this paper from 2009: Why are (the best) women so good at chess? Participation rates and gender differences in intellectual domains This paper attempts to explain ...
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1answer
44 views

Can the population be smaller than the number of possible outcomes?

Say a random variable $X$ returns one of the values $1, 2, ..., 6$. Conceptually, does it make sense to speak of a population, where each individual element is just $1$? In other words, does the ...
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27 views

Why are estimation results sharply different from the actual population (exponential distr.)

For my work, I analyze the field failure data sometimes and make decisions accordingly. (spare parts quantity, optimum preventive replacement point, ...) I made an experiment in Excel. Using inverse ...
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1answer
45 views

How do I calculate required Sample Size to get useful confidence interval length for Bernoulli random variables?

I am pulling meta data fields from a population of 100M documents. These meta fields include things like Author Name, Author Location, Keywords, etc. Some documents have all of these meta fields, some ...
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17 views

Measure of variance between two populations

I have a set of genes, each of which composed of $10$ values, $5$ coming from population $a$ and $5$ coming from population $b$. I would like to define a measure of the variation between the two ...
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30 views

Combining info from two population coverage levels from a tolerance interval

I have some existing product data from which I've calculated a tolerance interval with a 95% confidence level with at least 95% of population covered. I would like to use this tolerance interval as a ...
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62 views

When to Use Sampling Distributions And When to Use Regular Probability Distributions [closed]

Why/When would it be better to use Sampling Distributions such as the Sampling Distribution of the Sample Mean and why/when would it be better to use a Probability Distribution (such as Beta, ...
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1answer
24 views

Statistics - (bivariate data) Planning an Inquiry

I have to conduct a statistical inquiry that is representative of a population. You have to choose from a list of situations, and my choice was to measure the weight and length of carrots. The ...
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2answers
107 views

Why do we estimate population parameters using statistic?

I had been studying statistics, I have a doubt that I couldn't find the answer of. Its related to estimating population parameters using statistic. Suppose we have a population size of 10000, we want ...
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25 views

Compare two populations by their means… t-test?

I would like to have your opinion on the best way to compare two small sized populations of 13 and 14 individuals (but I have 3 tests for each individual on my dataset, so should I use 13 and 14 or 39 ...
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1answer
107 views

Why is the standard deviation of the sample mean less than the population SD?

The sample means do not vary as much as the individual values in the population. That the sample means are less variable than the individual values in the population follows directly from the fact ...
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19 views

Probability that difference between demand for two skills in a population sample is due to chance

I am trying to measure the demand for two skills in group of companies that are hiring software developers. One skill might be e.g. Java and the other e.g. C++. If out of 100 companies, 30 report they ...
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1answer
28 views

How can I show that my sample is random and a good representation of the population?

Okay, I'm looking at a population of user reviews. I have collected a random sample of the reviews and studied the trends of the words used and sentence structure. How do I make inferences about ...
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31 views

Performing a comparison between a sample distribution and population distribution in excel or nvivo

What is a relatively easy stats test to perform in excel/nvivo that is arguably reliable and valid and a good method for comparing a sample's normal distribution with a population's normal ...
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27 views

Estimating cutoff point for sampling using bootstrapping

I'd like to determine a cutoff point for plot sampling. So far, I've sampled intensively and collected fecal pellet data for 13 forested stands. Each stand has 50 plots and the mean pellets per ...
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1answer
52 views

Estimating age distribution from first names

Is it possible to estimate an age distribution of a specific population (e.g. actors, customers, etc.) from a list of their first names? Given that data of the number of individuals grouped by birth ...
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40 views

Finite Population Variance for a Changing Population

How does the addition of one unit affect the population variance of a finite population if everything else remains unchanged? What are the conditions such that the new unit leaves the variance ...
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123 views

Estimating number of balls by successively selecting a ball and marking it

Lets say I have N balls in a bag. On my first draw, I mark the ball and replace it in the bag. On my second draw, if I pick up a marked ball I return it to the bag. If, however I pick up a ...
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1answer
31 views

Resources for when population data is available

There are hundreds if not thousands of textbooks that detail how to make population inferences from sample. However for almost all my applications at work I have the entire population of data for ...
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32 views

Mixture distribution fitting for latent variable analysis

Are there any analytic approaches to using mixture distribution fitting for latent variable analysis? I'm specifically interested in existing approaches to determining whether mixture components ...
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14 views

Heterozygosity and the Wright-Fisher model

I was reading the textbook [Probability Models for DNA Sequence Evolution][1] by Durrett. In chapter 1, he discusses the Wright ...
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1answer
25 views

Assuming the true mean

I've collected fluorescence data from some bacterial cells. Each cell has a gene in it which can be induced to fluoresce. However, even without being induced, the gene will still fluoresce a little. ...
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30 views

Measure difference in answers on survey depending on item response options

For my thesis I sent out a questionnaire that has 10 questions. I set defaults: the first seven question had the default set to the desired answer and the last three questions had the default set to ...
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54 views

Interpreting coefficient errors in regression from uncertain population

I'm working on some regressions for UK cities and have a question about how to interpret regression coefficients. In a typical regression, one would be working with data from a sample and so the ...
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49 views

Multicollinearity in a “population model”

I was talking with a colleague who told me that at the time of making logistic regression across a population did not have to worry about assumptions such as multicollinearity, because when analyzing ...
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22 views

Learning theory for search data?

Has learning theory ever been applied in practice for search log data? If so, what are some findings about generalization/learnability from this data? I'm interested in generalization about an ...
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1answer
82 views

Do you need to report the standard error of the mean when the sample is the population?

The other day, my tutor told me that whenever a mean value is reported, the standard error of the mean must be reported alongside. But surely this isn't always the case? For example, let's say we ...
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49 views

Is a sample of 1961 people out of a population of 225,000,000 a sample size that is too small? If so, why?

I am working by a set of problems on a single question in my textbook. The question explained that there was a recent survey of 1961 adults out of a population of 225,000,000 and asked me to construct ...
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10 views

Use of multiple regression for data on 20 countries representing nearly the whole population

I have operational expenditure data for 20 countries (representing 90% of the whole population) which I want to compare with other variables from the countries (e.g. GDP, Population etc). Do I still ...
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2answers
86 views

Interpolating time series

what are best ways to interpolate time series? I have three data points(1980, 1990 and 2001) and I need to interpolate them. Using R na.approx doesn't seem to be what I need since the data I need to ...
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51 views

appropriate hypothesis test for non-negative quantity

This question is intentionally written in a very abstract way, because I am interested in a generic solution, or for pointers to different possible concrete cases in different fields: I am measuring ...
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23 views

Predicting the missing data out of three values in each of the two vectors [duplicate]

I have 2 vectors of rural and urban populations of the same country. (years from 1975 to 2020) with only three values (1980, 1990 and 2001 years) in each. And I need to predict the missing data. My ...
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1answer
52 views

Is it true that values of parameters do not vary from sample to sample?

This is something I was told. However, it seems to me that parameters of a population can be functions of time, in certain situations, in which case the values of parameters could vary from sample ...
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5 views

How to identify a subset of effects as the drivers of significant differences?

Okay I will explain this as best as I can. I have an additive risk score for each of my observations (i.e. I'm putting 100 individual effects into a single variable). The means of this risk score ...
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2answers
53 views

Have population, use inferential statistics? Also, non-normal dependent variable, what to do?

Background: We are looking at parental leave in Iceland. We are particularly interested in whether the economic crisis and the resulting changes in parental leave legislation affected the time taken ...
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25 views

Augmented split plot experimental design

I planned a field experiment with different genotypes according to an augmented design (check repeated entries plus unrepeated entries). Since I am testing a segregating population, each plot split ...
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49 views

Random variables: True or False

I sometimes get confused when reading statistical definitions when they mention random variables (RV). Are they talking about a single draw? Are they talking about an estimator? To make things clear ...
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66 views

Sampling probability

Say I start off with N single cells in a sample. These are then allowed to grow untill there are x progeny from each individual cell. How many cells must I take so that I have at least one progeny ...
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272 views

How do I detect the number of distributions in a set of data?

I'm trying to detect subpopulations of data in a set of data. The problem is that the data may have more than one subpopulation and the subpopulations may not be normally distributed. For example, ...