# Questions tagged [sample-size]

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

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### What is the minimum number of samples for the optimal performance of Gaussian Mixture Models?

I am using Gaussian Mixture Models and I noticed that they do not perform well when the number of samples per component is low. They might converge (due to low number of samples) but the inference ...
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### Weak Law of Large Number to Central Limit Theorem [closed]

Consider a distribution with unknown mean μ and population standard deviation σ=30. Using the Weak Law of Large Numbers, what is the minimum sample size in order to attain a probability of at least 99%...
43 views

### Best method of quantifying probability of new datum belonging to either of two distanced normal distributions?

I have two samples A and B from two separate normally distributed populations. The population mean of B is higher than that of A, but both are unknown. My aim is to find a threshold value between the ...
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### Different sample sizes, same population

This is a beginner question, sorry in advance if its super simple but i am a little stuck on what to do next I am using mean and standard deviation to analyze my data. I am working with the same ...
20 views

### Recommended sample size for t-test on non-normal data

I've come across a stats problem while working on my thesis. I ran multiple t-tests on a series of environmental parameters to determine if two groups of data are different (eg, early years vs. late ...
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### Can tests for balanced designs be used when groups have very similar (maximum difference of 2) but unequal sample sizes?

Example: 4 groups of following sample sizes: 21,20,20,19 Given that the difference in the sample sizes is relatively small, can tests which are suitable for balanced designs still be applied?
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### Ramifications of small + unbalanced group sizes, small number of groups for fixed & random effects models?

I have a variable (call it 'group') that I would like to treat as a random effect in a logistic regression. However, the number of groups is small (9 groups, larger than the recommended absolute ...
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### Sample size relative to true error

Say I have a distribution X, which is made up of n real numbers I have a subset K of X I also have two more subsets Y and Z, which each contain j samples from X How large does j have to be for the ...
68 views

### Penalized or standard logistic regression?

I am trying to conduct multiple logistic regression. My independent variable has 22 events (yes) and 310(N0) (total sample 332). I am trying to include 20 independent variables (to minimize ...
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### degrees of freedom in a t-test in Kruschke's BEST paper

This question is based on a comment by John Kruschke in his BEST paper, pages 589-590. Kruschke, John K. "Bayesian estimation supersedes the t test." Journal of Experimental Psychology: ...
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### Calculating required sample size using the effect size obtained from a (slightly) different population and exprimental intervention?

I am trying to work out an appropriate sample size for a study looking to improve the consciousness of vegetative state patients using low-intensity focused ultrasound stimulation as evaluated with ...
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### How to estimate the minimum required sample size to reach a certain significance level for a binomial test?

I'm about to conduct an experiment where I will measure a binary variable. I will test two different settings of a machine and then I want check whether these two settings yield different proportions ...
50 views

### Sample size for binomial distribution for rare events

I would like to estimate the parameter p in a binomial process but need to determine the sample size required. I believe the event is fairly rare, and I have read the normal approximation may not be ...
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### Derive standard deviation from mean, sample size and 95% CI

I am planning a clinical study and need to determine the needed sample size. My primary endpoint will be measured in blood pressure (mmHg). Many studies already exist for this, but they do not often ...
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### Why is minimum sample size not based on proportion?

In different situations there are many tests or general agreements for a minimum sample size, which are usually some fixed number that is not that high, capping at <400. Common numbers include 100, ...
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### Calculate sample size for linear regression [duplicate]

I have a total of 9 independent variables (IVs) and 1 dependent variable (DV). 2 of the IVs are binary and the other IVs are continuous ranging from 0 to 5. The DV is continuous ranging from 0 to 5000....
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### Sample sizes estimation for testing two proportions (2 samples): power based vs rewriting confidence interval

As I see it there are generally two ways to estimate the required sample size(s) based on what you want to test. For this question I am interested in a two-sample proportion test, where the binomial ...
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### n studies with multiple questions to be rated + minimum sample size for Cohen's Kappa using R

I'm new to Cohen's Kappa and have difficulty in trying to decide the right approach. So, I really appreciate if someone can guide me through this. Assuming I have 5 different studies (A-E) where I ...
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### Comparing logistic regression results for samples of different sizes

I'm working with a logit model that contains the following variables: Dependent Variable: Self-identification in the left-right political spectrum (dummy) Independent Variables: Age (continuous); ...
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### Combined variance estimate for samples of varying sizes

I'm working on my master thesis, and something's come up where I don't know if I'm "allowed" to do this and call it good science, I've scoured the internet to no avail of finding my answer, ...
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### How to Use Package “simsem” for Sample Size Determination in SEM: Validation Project? [Step-by-step Inquiry] [closed]

To provide context: My model is a latent model; 3 Latent Variables, 3 Indicators for each of two Latent Variables and the last Latent Variable with 4 indicators. Hence, Total of 3 Latent and 10 ...
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### Concurrent validity when the sample size of two populations differs much

I have two measures, the first scale was validated succesfully. Now, I want to validate the second measure by using concurrent validity. However, the first measure has the sample size of 300; on the ...
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### Sample size calculation with fixed sample size in one group

I am running a study to test the effectiveness of treatment A compared to treatment B. Given the study limitations, I am only able to recruit 200 participants into treatment A. The estimated incidence ...
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### Sankey Diagram: Sample Size Determination

I would like to ask your help on the decision about the best methodology to determine the sample size to conduct an observational study. This is a study in which it is intended to characterize all ...
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### Deriving formulae from clinical research publications

I am planning a research project with hypertension patients and am now trying to find the appropriate sample size for my clinical research proposal. I have found an interesting research project that ...
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### Does the size of the training dataset affect the AIC?

I'm conducting an experiment in which I want to compare the performances of 2 models. Both trained using the same algorithm (Logistic regression). I split the data ($n=10000$) I have into 3 parts, <...
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### Simulate data for multilevel & multivariate logistic regression

I want to simulate data for a multilevel logistic regression with several independent variables. I tried doing this with the steps of >>Arnold, B. F., Hogan, D. R., Colford, J. M., & Hubbard,...
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### What is the formula to determine the sample size for machine learning models?

I know that as a general rule the sample size needed to build a model using n independent variables is 10xn, however, is there a more accurate formula to determine the sample size?
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### How to simulate standard deviation

I would like to simulate data based on real data captured. The real data captured is 15 observations. The simulation based on the existing data is 100 observations. I have a mean and standard ...
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### Determining sample size from a Bayesian problem

I was following up on this problem when it seemed to me that the correct answer was ambiguous. I will not re-state the problem since it can be found in the original link. I will use the same notation ...
31 views

### Reagent batch change, sample size, results significancy

We are working on a biological protocol measuring a patient's feature using a blood sample. This protocol has proven to have some variability (CV <= 10%). During this process we sometime need to ...
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### How does a small sample size (underpowered study) affect the prevalence?

I am doing a meta-analysis where I calculate an overall prevalence value for multiple studies. I have submitted my manuscript to a journal. I used sample size as one of the risk of bias criteria, ...
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### Proof (requested) of sample sizes in multivariate distribution

My team has been asked to build a predictive model. We have a very limited dataset, but using a number of rationalizations about bounds on the data and the current behavior (54 data points) I have ...
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### Sample size calculation for linear regression model with random intercept

I am trying to calculate the sample size for a mixed linear regression model. The dependent variable is continuous and the model includes 2 further continuous variables. The random intercept is based ...
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### Sample size calculation for simple logistic regression. What's wrong with my code?

I want to learn how to calculate sample sizes for logistic regressions. Therefore, I want to reproduce the first example of https://www2.ccrb.cuhk.edu.hk/stat/epistudies/reg3.htm with P_1=0.4 (...
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### sample size calculation for testing classifiers

Normally when determining the sample size per group to see if two groups are different in their mean a power analysis (e.g. here) is used followed by a t-test (and p-value). I was wondering if there ...
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### moderate size of the data sample [closed]

It is often that the authors of papers in AI, ML and Statistics write that their methods are proved to perform good for "moderate sample sizes". I saw this statement in very high ranking ...
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### Translation of between-subject sample sizes to within-subject sample sizes

The following formula can be used to translate the sample size needed from one way between-designs (NB) to sample sizes needed in one way within-designs (NW): NW = NB(1 − ρ)/number of data points per ...
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### Formula for sample size for hypothesis test for difference in proportions confusion

For a hypothesis test for difference in proportions: Source A(Some Stanford professor): The sample size for both groups is $$\frac{2\bar{p}(1-\bar{p})(Z_\beta+Z_{\alpha/2})^2}{(p_1-p_2)^2}$$ \bar{p}=...
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### How to appropriately reduce data size or take a representative sample from it?

I have a spreadsheet file with around 150,000 pairs (x,y). I wish to work with a smaller file, i.e., with less data, so my exploratory analysis is faster. What is the appropriate way of resampling, or ...
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### Mann-Whitney test for unequal sample sizes

I want to run a Mann-Whitney test. But I got to know to know that for sample more than 20 we need to apply a different formula. My data sample is as follows. Group A contains data of 4 people and ...
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### Can trials have a differing number of samples when running PCA ? Why not?

Can somebody confirm that the number of "samples for each trial" doesn't matter(i guess that's right the language) for PCA. The case at hand is this: i have 5 sets of 3-dimensional ...
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### Sample size for Pearson's chi-square test of independence

I'm trying to do a $\chi^2$ test of independence between two variables. The problem I have is that I'm struggling with the sample size for the test. I always end up with some cells that have 0 samples....
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### Training data size requirements for imbalanced class classification

Our team is planning to start data collection for an imbalanced binary classification task. One in 30 cases is positive class and the rest 29 of the 30 cases are negative class. We have around 20 ...
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### Is the p-value dependent on n in case of paired student t-test?

I have a dataset where we believe there are a bunch of infected and uninfected subjects (total being 15). There are two ways to categorise these subjects into infected/ uninfected: 1. categorise 10 ...
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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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### A tail bound for an unknown distribution via sampling

I know that many results exist for making an argument about the tail of a distribution, i.e., for a random variable $X$, one can find a bound $\epsilon$ such that $\Pr[X \geq a]<\epsilon$. Some ...
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### marketing hypothesis test sample size calculation

I am trying to design a coupon promotion test to measure the increase in the volume of orders from promotion versus no promotion. To do so, I want to calculate the pre-group sample size required to ...