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

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21 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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17 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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33 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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16 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
49 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
30 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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25 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 ...
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1answer
41 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 ...
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2answers
62 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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16 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
35 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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50 views

To know clearly about the population

What is the difference among target population,study population and theoretical population ?
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59 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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40 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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80 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
48 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
84 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 ...
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1answer
103 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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18 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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62 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
51 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 ...
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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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52 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
53 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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110 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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67 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 ...
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2answers
219 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
109 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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54 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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40 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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77 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
166 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, ...
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1answer
91 views

How to accomplish unsupervised separation of subpopulations?

I have a dataset drawn from a social network that looks Bimodal on logarithmic scales for all attributes (I'll demonstrate only one here): I know the variable that would give me a clean separation ...
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2answers
210 views

Does it make sense to compute confidence intervals and to test hypotheses when data from whole population is available?

Does it make sense to compute confidence intervals and to test hypotheses when data from whole population is available? In my opinion, the answer is no, since we can accurately compute true values of ...
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1answer
168 views

Is my sample representative of the population I am trying to measure?

We have completed a survey of FTSE350 companies, but only received 49 responses. We assume that this response rate means that our results are not representative of the FTSE350 as a whole, but wanted ...
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4answers
2k views

SPSS: “Weight cases” by multiple factors, by taking the product of weights?

My understanding is that a sample can be adjusted based on a known population using the "Weight Cases" function in SPSS. What is the proper procedure for weighting by multiple factors? Let's say I ...
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4answers
205 views

Is any quantitative property of the population a “parameter”?

I'm relatively familiar with the distinction between the terms statistic and parameter. I see a statistic as the value obtained from applying a function to the sample data. However, most examples of ...
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1answer
40 views

How to best account for population sizes in disease outbreaks

Say one has the fatality and survivor rates of a pathogen in terms of geographical location (e.g., the latest data on the MERS-CoV). ...
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350 views

Population model to model year to year dynamics

My task is to assess how various environmental variables affect annual population fluctuations. For this, I would use a model like: $$ \mbox{log} ( \mu_{i,j+1} ) = \mbox{log} ( \mu_{i,j} ) + R_{j} + ...
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1answer
148 views

Population standard deviation for a binomial(?) distribution?

I have been confused by two separate questions (Stock & Watson - introduction to econometrics ch.3), using different values for standard errors. The first: In a survey of 400 voters, 215 respond ...
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3answers
234 views

How should I color scheme a heat map based off data below?

I have subdivided the globe into 100 sq mile bins and then collected how many tweets were sent with a geolocation within each bin. At first I color coded each bin on the map based off a standardized ...
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65 views

Combining covariances

Imagine we have one sample (n=40) from a population on 2 variables, for which we estimate the covariance (say, 0.1). If we would have another sample (n=10) from the same population, and we estimate ...
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2answers
49 views

How do I give a larger weight to a smaller population?

I have a set of cities ranked 1-10 based on several criteria. I also have the percentage of the total population living in these cities. I want the cities with smaller populations to be able to ...
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47 views

Fisher's exact test for comparing 2 years of population data?

I am a young ecology graduate student who is starting to learn statistics. I've already collected some data on our study populations that my adviser has asked me to analyze. There are 20+ populations ...
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3answers
239 views

Best method to analyse whole population data

I have data of an entire population (N=27). I would like to find out which variables (of many) have the greatest effect on one certain dependent variable, and how much of its variance can they ...
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2answers
242 views

are there any statistically significant differences between my study population and a sub-group within it?

I have a total population of 31, of these I have a treatment finishing population of 20. I want to run a test on SPSS to identify if there are any significant differences between the 20 individuals ...