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

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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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7 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
56 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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34 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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20 views

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

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
37 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
39 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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12 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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36 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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1answer
60 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 ...
3
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1answer
104 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, ...
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23 views

Finite Population Correction Factor

A simple random sample of 21 observations is drawn from a finite population of 41 individuals. If the population mean is 300 and the population variance is 7, then after applying the finite ...
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1answer
28 views

Question Regarding Statistically Significant Population Attributes

I have a problem I am trying to solve with the Chi Squared test, but I am starting to realize there are probably better methods to use, and I was looking for suggestions. Say I have two independent ...
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1answer
38 views

Spearman's rank correlation coefficient over population

I have a data set composed by 2.000.000 projects, each of them is defined by the number of active users and the size (KBs) of the project. I would like to check whether a correlation exists between ...
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20 views

Linear mixed model when interest is ONLY in population

Lets say we have 1 to 6 repeted measures over time for some (many) subjects, and the outcome is values between 0 and 23 (so we assume normal distribution). For a normal distribution the fixed effects ...
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46 views

How is this version of the pearson correlation coefficient derived?

After taking my first semester stats class I started getting more and more into statistics. Currently I've come across this version of the Pearson Correlation Coefficient. Comparing this formula to ...
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32 views

Comparing a subset of a population with the entire population?

Is it possible to compare and test actual subsets of a population to the entire actual population? That is, let's say for a baseball team we want to know which players are contributing to the team's ...
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1answer
53 views

What are the consequences of knowing (or not knowing) the range of possible answers from a test

Lets say we are interested in some unknown variable x. We poll a x at different intervals and get a set of values that x has been. However we know that if we poll x enough times we will eventually get ...
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1answer
34 views

What benefit can be gained from finding total population size

I would imagine this has been asked before but I can't find it so feel free to link if you can! Lets say I have a sample size of 100 and an unknown population size. There's a great deal I can learn ...
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32 views

$R^2$ in multivariate regression

I'm trying to determine how the population $R^2$ value is defined in the multivariate regression model where we have $Y_i = \mu_y + B^\prime(X_i - \mu_x) + err$ Where $Y_i \in \mathbb{R}^q$ and ...
5
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1answer
62 views

What does the “different populations” result of a significant group t-test mean exactly?

Why does finding a significant difference on a given measure, say mathematical ability, between two groups (e.g., via an independent samples t-test) have to be equivalent to the two groups coming from ...
2
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2answers
126 views

Z-scores, standardized tests and population means

I have been using z-scores by subtracting the mean (and then dividing by the SD) of the sample, whereas I recently read they actually need to be the population mean and SD. Assuming you are ...
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1answer
50 views

What is the Australian Calculator?

i need to know how to use the Australian Calculator to get my sample size. i was instructed to carry out my research using the Australian Calculator, but i don't know what it means.
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17 views

Sample/Null Value

I was running through question section on my stat book and the following question was posed: If our sample value is close to the null/population value, we conclude that ... I don't get if that ...
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61 views

How useful are per capita calculations in level of education of a population?

I had a discussion recently in which it was stated that Scotland having more universities in the top 200 per capita than any other country is a good indication of the intelligence of the population of ...
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1answer
39 views

Is my data representative of Bristol?

I've got some data about people in Bristol. I have about 75,000 records. Part of my dataset is each respondants age. Aside from this, I have also downloaded census data for Bristol, which gives me ...
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66 views

To know clearly about the population

What is the difference among target population,study population and theoretical population ?
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63 views

Why is 30 touted as a sample size when the tables say otherwise?

If I have a population of 5000, statistics suggests that I need to sample about 350+ to get a confidence interval of 95% with margin of error 5%. So why do I see that sometimes we can get away with ...
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41 views

Finding overlap in two similar populations

I run a few different projects throughout India and want to understand how many unique individuals I've provided services to total. I don't collect names or unique identifiers, so all I know is a) the ...
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2answers
110 views

Whether the population exists in an experimental study?

In my oral exam one of my teachers asked whether the population exists in an experimental study. I answered: "Yes. the population exists in an ...
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1answer
52 views

What test of significance should I use to analyse visits to a clinic by various groups?

Apologies for the noob question. After a day on Google and Wikipedia I still can't quite work out what to do. So here I am. A small private healthcare clinic in the UK has asked me to look at their ...
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1answer
102 views

Interaction variables work differently when population is split

Let's say I have two predictors to predict financial risk: Gender and shopping habits. Gender has levels of "Male" and "Female", while shopping habits has "quick shopper" and "slow shopper". I am ...
3
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1answer
116 views

How to compare sampled areas to the Census?

I would like to discriminate sampled areas that are representative or not representative of their corresponding population, for a given characteristic. Suppose I have surveyed areas (i.e. Census ...
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22 views

What are appropriate statistical test to compare historic Census variables for different locations?

I am wondering if anyone has suggestions on which statistical test would be appropriate to compare demographic data obtained from 1900 Census schedule sheets? I have a database of boarding school ...
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19 views

Applying the distribution of a large sample to estimate probability for a smaller sample

I have the sample size, mean and standard deviation for the number of births per year for my county, but I'd like to transfer that information to a smaller population within the county (ie. a school ...
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78 views

Testing to see if a population is normal?

I'm an amateur statistician. I do it mostly for fun. I'm finishing up on my first semester stats class that covers up to hypothesis testing. I'm planning on beginning learning simple regression ...
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2answers
62 views

Sampling from a dynamic population

I need to create a sample of a given size from a population. However, the population is dynamic, that is, comes as a stream of items, and every item has a "time stamp" based on its location in this ...
3
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1answer
75 views

Why describe a sample as i.i.d.?

I’m hoping for some help understanding the concept of RVs with respect to their use in the theory of drawing inferences on a population from a sample. To draw inferences on a population using a ...
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61 views

Need to verify sample is representative of known population of animals

I'm a biologist trying to verify that the age, gender, and family group of my samples from a population of whales is representative of the population, in order to make inferences in the discussion. ...
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1answer
54 views

For a research project I'm trying to estimate how many videos currently exist on Youtube

Official stats on how many videos (rather than how many hours or what volume of data) seem quite hard to come by. My current idea is something like this: A youtube URL is like: ...
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3answers
134 views

Standard Deviation and Variance in Sample and Population Formulas for all?

What are the differences between those Population and Standard Deviation and what are their fomulas? I was told that they are different formulas and which situation do you use population or sample? ...
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15 views

Quantitative ,longitudinal, observational study:Population, sample and instrument

I am studying US public company financial performance for the last 2 decades. I am searching for evidence of "sustainable superior performance", thus to isolate those companies that display such ...
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77 views

When do we calculate the population parameter instead of sample statistics?

When do we calculate the population parameter instead of sample statistics? If there is a this kind of case which statistical tool should we use population parameter or sample statistics? A car ...
3
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2answers
304 views

How to combine data from 5 surveys from the same population spanning 10 years

I have results from 5 surveys each 2 years apart and let us assume that no subjects are selected in more than one survey. The sampling method used in these surveys are biased and I have sampling ...
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2answers
148 views

How to deal with non random samples?

I have a specific question about random selection, representativeness and inference. It is well known that it's necessary to use random selection to get representative samples from the population of ...
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60 views

Can you make population inferences from two different samples of the same population?

Say that 100 police-trained dogs were chosen and randomly divided into two groups. One group would be kept with trainers who don't expect the dogs to get too trained and the second group is kept with ...
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52 views

Appropriate way to estimate sample size requirements for an unknown population distribution

Assuming we have a sample (some observables) from a population of unknown distribution, can I assume that the right way to estimate the sample size (for estimating means, medians, etc.) is using the ...
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90 views

How do I weight population statistics in SPSS?

I'm struggling with analysing my survey results in SPSS and really hoping you can help. I surveyed occupational therapists around aspects of their practice, on a national level and the seniority of ...
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3answers
200 views

How to report data for an entire population?

I am conducting a descriptive study, and I am using the entire population in my study and not a sample. I understand that everything I am reporting is a population parameter at this point. However, ...