# Questions tagged [sample-size]

This tag is ambiguous. Use it when the question is about sample size and NONE of the following are more appropriate: [small-sample], [large-data], [statistical-power], [underdetermined], or [unbalanced-classes].

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### Calculating a sample size based on the target width of a confidence interval with stratification

I am reviewing a sampling design devised by a colleague and completely fail to understand it, although I am not a novice in statistics (but not a huge expert either). The said colleague is no longer ...
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I'm struggling with a contradiction when trying to determine a sample size when proportion is small. If I use binomial formula: $n = p(1-p)z^2/ME^2$ then the smaller the proportion - the smaller ...
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### GAM sample size

A common rule of thumb in social science is to have at least $30$ observations for regression (without any complicated effects). Does someone know such rule of thumb for GAMs? Are $50$ observations ...
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### How to compare model fits between datasets of different sizes?

A measure like mean square error appears to tolerate some variation in dataset size but, for example, a two-parameter model is still likely to produce a great (yet meaningless) fit to any dataset with ...
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### What are appropriate statistic tests for top-down and bottom-up knockout experimental designs?

This concernes a two staged experiment on cell toxicality. A: Aim is to find the lowest concentration of the toxic agent 'CTA', that kills the target cells with at least 99% security. Use of lowest ...
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### Why there is no agrement on power / sample size for factorial repeated measures design?

I'm not really sure to what degree this is a statistical question but thought this might be the best place to start. If my questions prove only my ignorance please vote it down and I'll delete the ...
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### Samples size with sample proportion close to 0 or 1

For a future monitoring program on small water bodies we want to calculate the sample size. The bodies of water are so small that their number easily exceeds 100.000 in the monitoring area and ...
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### Appropriate sample size for weighted sample

I have a population that is sampled such that each item has a different probability of being selected. That probability is separate and independent of the value of any given item. How do I determine ...
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### choosing sample size in prevalence study with a finite population

I am looking to conduct an epidemiological study on a population of 1000 individuals and need to find the appropriate sample size. So far, I have the parameters to calculate my sample size but I am a ...
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### Are a distribution's higher-order features harder to estimate?

In what sense, if any, are a distribution's higher-order features (e.g., moments, cumulants) harder to estimate than its lower-order features, for at least some distributional families? For example, ...
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### How small is too small to fit a reasonable long memory model?

When looking at papers about long memory they tend to analyze data sets whose length is in the thousands, see http://www.math.canterbury.ac.nz/~m.reale/pub/Reaetal2011.pdf for an example. My question ...
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### How do you experimentally determine a minimum sample size to characterize a response?

I want to repeatedly perform a measurement until the distribution of response values stabilizes. Is there a standard metric to stistically conclude that new data does not contain new information? I ...
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### confusion about the link between residuals, error terms, sample size and CLT in ANOVA

I feel a little confused about the assumption of the ANOVA and what it ensures mathematically the errors have to be iid and normally distributed N(0,1). independance of observation. Is it not a ...
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### Required size of control group for two-proportion z test

How do I determine, pre-experiment, the minimum size of a control group that would be needed to satisfy the requirements of a two-proportion z-test? $p_i=\frac{k_i}{n_i}$ is the proportion of ...
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### sample size calculation for interrupted time series

I am trying to do a sample size calculation for a interrupted time series study design. I am reading Zhang's simulation-based power calculation paper and this one. It seems to me that for a time ...
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### How does the size of my sampling grid affect my required sample size

I would like to know how sample size estimation is affected when the categories are artificial rather than naturally occurring and clearly discrete. In my scenario I'm using a grid of a certain size ...
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### small sample size mixed model analysis

My question is regarding the minimum sample size needed in a mixed effects approach for analyzing a main effect. Lets say that a sample is taken of n=8 subjects with k=10 measurements of a ...
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### Sample size calculation when observations are subject to percent errors

I'm trying to find a way to calculate the required sample size for an experiment in which the observations are subject to measurement errors expressed as a percent value of the observation. For the ...
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### Confidence interval for mean of highly skewed distribution

My background: I have completed an introductory course in statistics and done some further reading on my own. I have 3 months of R experience. I have been asked to design an experiment to measure the ...
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### How to check the assumptions behind an inference procedure, in the case of very large data sets

On this site it has been confirmed multiple times that, contrary to what is often heard, hypothesis tests don't have any issues with large sample sizes. As a matter of fact, the probability of Type 1 ...
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### Minimum sample size for multiple choice question

I have a question about minimum sample sizes for a multiple choice survey. I have searched around this site and the internet, but haven't found a 100% clear answer yet. What if someone a survey was ...
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### Sample size formula for multiple regression between binomial variables?

Let's say we have k binomial variables, and a sample size of n observations per variable, where each variable occurs (positive case) at a given frequency/probability f. We would like to check if ...
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### Can survey sample sizes be used for quality control sampling? Is the formula that easy?

I have no solid background in statistics so please bear with me. In general, I am trying to figure out methods to determine sample sizes required to establish a certain level of confidence for a ...
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### One-tail versus two-tail z-score

In calculating minimum sample size one must specify, inter alia, z-score. I am estimating a min sample size for an accuracy rate. As I only care if the accuracy rate is lower (happy if it is higher) ...
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### How to calculate MoE for subsamples

I have demographic and income data for 3 million people from the American Community Survey (courtesy of IPUMS), and my goal is calculate the median income for every permutation of age group, gender, ...
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### Logistic regression power analysis with moderation between categorical and continuous variable

I've been reading Simulation of logistic regression power analysis - designed experiments, http://sas-and-r.blogspot.com/2009/06/example-72-simulate-data-from-logistic.html, and Power analysis for ...
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### Why do I get difference results when using pooled ols and random effects model?

I was wondering what the difference between pooled OLS and random effects model is? I know that random effects eliminates the time-constant effect. However, when i run my regression with pooled ols ...
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### How to run a power analysis for a repeated measures (all within-subjects) with combined contrasts?

I am looking for a little help on determining the correct way to run a power analysis on a within-subjects repeated measures design (i.e., no between subjects variable) with combined contrasts. ...
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