# Tagged Questions

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

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### 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 ...
4k views

### Locating freely available data samples

I've been working on a new method for analyzing and parsing datasets to identify and isolate subgroups of a population without foreknowledge of any subgroup's characteristics. While the method works ...
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### 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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### 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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### How do I work out my sample size when taking several different measures?

I have looked at a lot of different methods of calculating my sample size but none seem to fit with my study design. I am classifying farm animals into 4 groups based on observations at 4 time points ...
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### Does transformation of r into Fisher z benefit a meta-analysis?

Usually $r$ is transformed into Fisher $z$ to test difference between two $r$ values. But, when a meta-analysis is to be performed, why we should take such a step? Does it correct for measurement ...
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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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 ...
52 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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### 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 ...
108 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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### Confusion between sample and population

A team has conducted a study in which an introductory class was randomly divided into two groups. Group 1 was administered a dosage of alcohol. Group 2 was given an equvialent dosage of ...
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### 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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### 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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### 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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### 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 ...
11k views

### What is the difference between N and N-1 in calculating population variance?

I did not get the why there are N and N-1 while calculating population variance. When we use ...
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### 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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### 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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### Whether to use r-square or adjusted r-square with a small sample size that may represent the entire population?

I read online that it is only necessary to use adjusted-$R^2$ when you are working with a sample rather than the entire population. The data I'm working with is information on a series of live ...
215 views

### Is there a way to compute diversity in a population?

Say we have the following 5 cities, each with the same population CityA with 20% each of 5 ethnicities CityB with 99% of one ethnicity, but 100 different ethnicities in the remaining 1% CityC with ...
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### 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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### 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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### 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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### 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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### Good distribution for modelling age in a population

What is a good distribution for describing the age structure of a population? For example, if I want to know the probability that a member of a population is less than or equal to 20. How can I ...
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### 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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### 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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### 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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### Conditional fixed effects Poisson *with population exposure*

Reading a paper, the authors use a "Conditional fixed effects Poisson with population exposure." I wasn't sure what "population exposure" meant, so I looked it up. It seems like the term comes from ...
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### 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 ...
173 views

### Population Variance and Sample Variance

How is it that lowering the number of frequence,$n$ by $1$ in the for formula for Population and Sample Variance account for the discrepency of using sample rather than population. I mean how is ...
122 views

### Population vs sample variance

This is perhaps a very basic question, but I am a bit confused. I have a time series of day some time varying data, say the amount of sunlight as the day passes. I bucket the data in say 10 bins say ...
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### Mixing User Data For Cross-Validation

I have data from 12 users, and want to perform cross-validation. Is it necessary that I create my training and test data from different users, or can all of the data be randomized, and then split into ...
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### Is a chisquare on a (nearly) complete population data necessary?

I have data from a survey that was (attempted to to be) administered to all children of particular grades in a certain state. I am getting it after a cleaning step by the survey designers that removed ...
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### Sampling distribution of means

Im working through a textbook atm and Ive read that the mean of "the sampling distribution of means" is the same as the "populations" mean. To construct the sampling distribution of means, i need to ...
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### What does population actually refer to?

This is probably going to sound extremely stupid, but it's part of a larger question, about sample distribution of means, that I'm having problems understanding, so please bear with me. If I record ...
202 views

### What is the mode of US height, in inches? What percentage of americans does this mode represent?

I am setting the starting-height of a console, and so I would like to know what the most common height is, and what percentage of americans the console would not have to move for. I am shocked at how ...
115 views

### What does “return rate” mean in population ecology models?

What does "return rate" (tasa de retorno in spanish) mean in population ecology models? In context of capture-mark-recapture models. I have found many articles on ...
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### The statistical prevalence of solely negative genes in the adult human population?

I really hope I'm not asking this question on the wrong stackexchange site, but seen as this question has a lot to do with statistics I'm guessing I might be in the right place. There are certain ...