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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31 views

Sample size calculation with different standard deviations

when calculating the required sample size with a given power and p threshold, usually the calculator only requires two estimated population mean and standard deviation. is it always valid to assume ...
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Optimal Allocation Proof [duplicate]

I'm trying to derive the optimal allocation formula for but I'm not sure where I'm supposed to start with the derivation. If anyone can help point me in the right direction, that would be greatly ...
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22 views

Optimal Allocation Proof [closed]

I'm trying to derive the optimal allocation formula for but I'm not sure where I'm supposed to start with the derivation. If anyone can help point me in the right direction, that would be greatly ...
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1answer
30 views

Proof an equivalence of variance

Given a sample of size N, how can you prove this? $\frac{1}{N}\sum_{k = 1}^{N}(x_{k}-\bar{x})^{2} = \frac{1}{2N^{2}}\sum_{k = 1}^{N}\sum_{l = 1, l \neq k}^{N}(x_{k}-x_{l})^{2}$ So far I have: $$ \frac{...
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1answer
28 views

How to determine minimum sample size @ 95% confidence for binary outcome

I'm not a student -- I'm working on a presentation for work. I've spent hours searching for a calculator that will do this but to no avail. There are 100 marbles in a jar. The marbles are either blue ...
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1answer
9 views

Statistical test to find differences between percentages without knowing the size of one population

I need some help. I am making a comparison between the percentage of responses to a questionnaire in my target population (N=210) and the responses at a regional level to the same questionnaire (the ...
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0answers
17 views

How to interpret effect sizes in simr power simulation for mixed models?

I am conducting a power analysis for linear mixed models. I want to know what sample size is needed to find a specific effect size for an interaction. I am testing the interaction effect by comparing ...
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1answer
56 views

Power simulation (a priori) for mixed models when no prior data is available

The recommended way to do a priori power calculations for linear mixed models is to simulate data and then estimate power using the simr package, for example. All these approaches require you to ...
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1answer
68 views

Comparing 3 independent proportions (categorical)

I want to compare the proportion of correct answers. My variables are categorical (group condition type and answer) and my answer options are dichotomic (one trial, one question - correct/ wrong). ...
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Tight error bound for Possion sampling to estimate a real-valued mean without knowledge of variance

I am trying to develop a tight bound on the sampling error of a Poisson sampling (sampling with non-uniform probabilities). I have a set of real-valued data $X$ with finite size $N$ and I want to ...
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2answers
27 views

Estimating sample size required from previous study

Suppose I have a two phase experiment. The goal of the experiment will be to test if there are differences in proportions between two treatments. In phase one, I have no idea how many samples I will ...
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How many games do I need to play to know how good each card is?

I play a game called Hearthstone. Here are the important rules of the game: There are two players. On each player's turn (called a ply), they draw 1 card to their hand from their deck of thirty (30) ...
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How does a smaller sample size affect False Acceptance Rate?

We have a theoretical document describing $x$ amount of audio samples pertaining to a speech recognization project. The document specifies certain ideal targets for FAR and FRR. Specifically: FAR ->...
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Bernoulli sampling method estimator

Let $t = N\bar x$ be an estimator of the total of population in a bernoulli sampling method where $$\bar x = \frac{\sum_{k = 1}^Nx_kI_S(x_k)}{\# S}$$ $\# S$ is the size of the sample. Prove that $E[t] ...
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Correlation testing with ordinal variables of different sample sizes

I have a dataset of several building complexes with the corresponding number of maintenance requests (response variable). The quality of each house in a complex is ranked from 1 - 6 with 1 being the ...
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1answer
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Sample calculation from a big population [closed]

I would like to calculate my sample from a working population of 583 890. The population mean and standard deviation is unknown. The confidence interval has been selected as 95%. Kindly help Kevin
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5 views

Sample size calculations for a mixed effects model using the R library sjstats

In using the sjstats function smpsize_lmm() in R, to calculate a sample size for a two level, mixed effects model. I am getting results I can't explain. Here is the code I have used and the results ...
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0answers
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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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0answers
19 views

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%...
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2answers
49 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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10 views

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 ...
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1answer
32 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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5 views

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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1answer
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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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7 views

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 ...
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1answer
71 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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1answer
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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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1answer
25 views

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 ...
2
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1answer
59 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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1answer
32 views

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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0answers
16 views

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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0answers
17 views

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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9 views

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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0answers
15 views

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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0answers
13 views

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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1answer
22 views

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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0answers
24 views

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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0answers
8 views

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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1answer
15 views

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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0answers
14 views

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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0answers
13 views

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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1answer
22 views

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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0answers
17 views

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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1answer
27 views

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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3answers
505 views

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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1answer
54 views

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 ...
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1answer
33 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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1answer
21 views

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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0answers
38 views

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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