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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17 views

Sample complexity of quantile approximation

I was looking into the sample complexity of $\epsilon$-approximate quantiles. The problem is defined as when having distribution and looking for quantile $\phi$, one has to answer with an element ...
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20 views

How can I calculate sample size for case control study?" [closed]

Please, I want to understand how to calculate the sample size the formula for the project entiled, "Evaluation of renal function in type2 diabetes mellitus patients attending federal medical Like&...
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1answer
55 views

What batch size should I use to estimate the multivariate effective sample size (multiESS) if I have virtually no autocorrelation?

I am trying to estimate the multivariate effective sample size of an MCMC posterior sample with 8 parameters. For that, I am using the function multiESS in the R ...
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11 views

Sample size calculation for Difference in difference

We are planning to launch a causal experiment - in which one group gets t (treatment), while the other group gets c (control). So assuming that we have our pre launch number in each group (denoted by ...
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12 views

sample complexity vs training cost (time complexity)

I have a question about the complexities. Consider two regression problems A, B and assume that A has lower sample complexity than B. A and B share the same target function but the loses are slightly ...
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21 views

Are there quantitative methods for determining sample size for SVM?

Are there any quantitative and justifiable methods to help choose minimum sample size for having a 'good' model from SVM? Logistic regression affords power analysis which provides minimal $n$ to ...
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22 views

fMRI: Is there a minimum sample size for performing Principal Component Analysis for dimension reduction? [closed]

I'm performing a functional MRI study and I need to analyze the relationship between 198.350 variables (connectivity between pairs of brain areas) with certain condition (1/0), in a sample of 90 ...
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1answer
35 views

What are the ways to normalize the vegetation data when the plot sizes of samples are different?

I have collected data on mangrove tree species density and composition from two habitat categories (sample groups) by using belt transects of various lengths between 100 x 10 M to 500 x 10 m. (3 & ...
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1answer
36 views

Sample size required for a given margin of error in sample mean when population standard deviation is not known

I have trained a regressor to predict the revenue generated when users click on an ad impression. Only few clicks eventually lead to positive revenue. As such, I have used the Tweedie regression in ...
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7 views

Effectiveness checking of control plan / implemented corrective actions

I have a question about statistics for a manufacturing environment. I work in a heavily regulated environment for medical devices, as a manufacturing engineer, but statistics is not my strong suite. ...
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1answer
31 views

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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1answer
78 views

Which statistical analysis should I perform if the data sets are not normally distributed?

I am doing an experiment where there are two independent groups; one is the group of "infected" patients another is the group of "sepsis" patients. I am comparing "platelet monocyte aggregates(PMA)" ...
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7 views

Is there a rule-of-thumb for number of variables included in a model relative to sample sizes of your primary comparison groups?

I am constructing an analysis plan for a retrospective cohort study in which all relevant subjects (i.e., met inclusion/exclusion criteria) from a large data base were chosen. The resulting group ...
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18 views

Correlation with variables with small differences in sample size

I have a sample of people, around 1140 participants but not all of them answered all questions. I have to do correlation with variables , each with different sample sizes. I have 3 variables and they ...
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1answer
18 views

Calculating Duration of AB test for measuring sales change in stores

I have done my research about AB testing an seen that it is usually implemented in the online space(websites etc), I am trying to implement the same concept but at a store level. Problem: Given a ...
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28 views

Sample size calculation for AB testing in offline scenario

I have sales data for 500 stores and lets say I want to run an AB test on a sample of test and control stores with the objective of getting statistically significant increase in sales(lift). My ...
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1answer
36 views

Number of samples needed to estimate population mean to given margin of error

The population distribution is unknown, but is probably multi-modal. The required margin of error is given in advance. Any number of samples can be drawn from the population. Given enough samples, ...
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5 views

selecting number of folds in an unevenly distributed small dataset

I'm working on a facial expression dataset with 7 classes with the following sample distribution. I'd like to perform a k-fold but some classes have less than 10% number of samples than the largest ...
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25 views

Confidence Interval for a sampling P95 in unknown distribution

TLDR: I need to estimate what is the minimum sample size to get a W-wide confidence interval of daily Response Time's P95 of which I only get a sample of events. Detailed: Due to a Service Level ...
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12 views

Sample Size Guidelines for KS-Test and AD-Test

so I've been looking into the Anderson Darling and Kologorov-Smirnov test because I have datasets with a large number of observations (~6000) and would like to fit distributions to them. They are ...
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50 views

Minimum number of observations per variable for PCA

We are working with a dataset that includes 35 individuals (i.e., sample size). Each individual has a minimum of 1 session (i.e., row) where we recorded the proportion of time spent doing a behaviour ...
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23 views

How to deciding on the number of experimental runs in R for orthogonal fractional factorial design?

Presently I am working on designing a questionnaire for my discrete choice experiment. I want to generate an orthogonal fractional factorial design for the following problem- The respondent has to ...
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1answer
140 views

R models with unequal sample size

I am currently running GLMM in R for comparing correct response and response time in two groups (patients and control), each composed of males and females. I have 3 variables: Group, Sex. (inter ...
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70 views

Sample size and number of Samples?

I have come across two major problems recently, and couldn't solve them. Imagine we have measured an independent variable 2000 times and I'm interested to talk about the mean of the population: So as ...
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10 views

Why sample ratio mismatch is important?

In performing hypothesis tests we always include the sample sizes, so why is ratio of sample size important and can you please help me with an example where it could skew the results. Thank you
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15 views

Sample size determination with three levels of sensitivity

I am looking to conduct a one-sided cross-sectional clinical study with dichotomous (immune/not immune, with no gray area) variables and an analytical test that has specifity of 99.81 % (99.65 – 99.91 ...
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2answers
157 views

Linear Discriminant Analysis have Small Sample Size problem (SSS) is it n<<d

It is said that LDA has a Small Sample Size problem (SSS) This problem arises whenever the number of samples is smaller than the dimensionality of the samples. (Source: Chen, L.F., Liao, H.Y.M., ...
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20 views

Choosing sample sizes when working with different sensitivity levels

I am currently ramping up a project to determine the rate of immunity in a population with SARS-CoV-2 using the new Roche Diagnostice test kits. Now, we will be testing people over the course of 6 ...
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30 views

Determination of sample size for a Kendall's tau correlation, one variable ordinal and the other continuous

I'm a bit stuck at the moment. I have a study where we are comparing a new method of strength measurement that will give output in lbs of force versus the standard methos of grading it on a 0-5 ...
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23 views

tolerance interval, sample size and power

I can only find limited information on how to calculate sample sizes in respect to tolerance intervals. I have a particular problem I would appreciate any help on. If I had a normally distributed ...
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15 views

performing a multilevel logistic regression: data naturally clustered but small clusters, singletons and limited number of 2nd level clusters: help?

I am looking to perform a binomial regression calculating the reselection chances of parliamentarians in the European Parliament based on their activity levels. DV= reselection: 0/1. My data is ...
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1answer
17 views

Calculating the optimal sample size before running a test

I want to run an experiment to test the outcomes of variations A and B. I'm designing the experiment but I want to know what's the minimum sample size to obtain a result of 10% difference between ...
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1answer
116 views

How should an Auditor determine the minimum sample size?

Let's pretend that in a Financial / IT / Construction Audit of a task which the outcome is either Pass(1) or Fail(0). Suppose that the Auditee should perform this task on a daily basis (365 days in ...
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20 views

Calculating sample size required to test (power?) of tool

I have a tool that is designed to help people solve a puzzle. I want to see how good it is at helping people to do this. I thought I would start with taking a group of people and getting them to test ...
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32 views

Why are normal quantiles used for sample size calculations instead of the t-distribution?

The sample size formula for a one-sample t-test is often given as: $$ n = \frac{(z_{1-\alpha/2} + z_{1-\beta})^2 \sigma^2} {\Delta^2} $$ Meanwhile, G*Power appears to use the t-distribution, which ...
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26 views

Sample size when looking for a rare attribute

BASED ON THE EXCHANGE OF COMMENTS OF BELOW, I KNOW REALIZE THIS THE WRONG QUESTION I know similar questions have been asked, but I haven’t been able to find a satisfactory answer. I have a ...
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35 views

How to estimate the required test set size for multiclass classification

Due to weird circumstances I have: 50,000 data points to train a model on. These data were not sampled randomly from the population, so I can't use them for my test set. 500 randomly selected data ...
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11 views

Tests of the effects of variables on imbalanced categorical variable [duplicate]

I have survey data that include a binary response variable,say y, and various theoretically relevant independent continuous variables. y is binary, which includes two options, say Option A and Option ...
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55 views

Can the size of the training set of a neural network be smaller compared to other models?

If some of you knows what is the rule thumb one in ten rule this what I want to discuss. Neural network can, nowadays, go deeper in performances. Did you find, according to your experiences, that you ...
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1answer
26 views

Relating $\alpha$, sample size ($n$), and power

I've seen in R-programming a pwr package (full disclosure, I don't know how to code or program). I was wondering if there is a formula and if possible a link to its derivation that lets you ...
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1answer
41 views

Does a post-hoc power analysis suffice in a psychological paper?

I am a psychologist and I have the following question: Last year I was running a study. I intended to collect at least 400 participants (the anticipated effect size was hard to estimate). The study ...
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1answer
92 views

How to detect sample size for multiple groups in an AB test?

I'm sure you know this sample size calculator by Evan Miller. Given necessary parameters, it outputs the efficient sizes for Control & Test groups. But what if I have multiple Test groups? What ...
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9 views

Need to reproduce the Sample size

I am currently working on reproducing the sample size of a prospective cohort study using a standard WHO's protocol. The protocol reads "Sample size calculations for this study are driven by the ...
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23 views

sample comparison, sample sizes and logistic regressions

I have conducted two surveys, one representative sample (n=100), where set quotas for demographics, etc. (it is balanced out) and I did the same survey with a group of specialists (n=60), which is ...
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11 views

How to calculate sample size of a study with difference in median as primary outcomes

A quick question on sample size calculation. How to calculate the sample size for a study in which the primary outcome is a difference in the median time to improvement (e.g. 10 median days in group A ...
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16 views

Minimum subgroup sample size

I have a population-level data set of continuous data, where a column represents a single individual and a row represents the measurement of the variable in question. Given the scope of the data, I ...
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36 views

sample size calculation for intraclass correlation coefficient (ICC)

I want to design a study when I'll be comparing three measurements of a variable in imaging and then compute an ICC as a measure of agreement since I'll be obtain a continuous measurement. I read ...
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1answer
35 views

Why is the suggested sample size much larger than what's necessary for significance?

Imagine you're doing an A/B-test in Marketing. You send a control group the standard e-mail, and a test group an e-mail in which one element was changed (for example the color of a button). You want ...
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2answers
32 views

Size of the sample

What will be the size of sample as compared to population size that we considered it as large sample/ small sample? Sometimes I see that if n=24 it considered as large sample and sometimes even for ...
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1answer
23 views

In a logistic regression model focused on prediction, what are the problems associated with a big difference in the sample sizes of a binary variable? [duplicate]

In short, I'm curious about the problems associated with a difference in the sample size of respondents by a binary variable when fitting a logit model focused on prediction rather than causality. By ...

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