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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How to select or estimate unknown population proportion p for hypergeometric distribution using results of previous experiments?

There is monthly quality control process. 1000 reports were generated in May. I need to calculate sample size, verify it and made the conclusion whether there are less than 2% of reports contain the ...
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z score total for fixed alpha and beta in sample size calculation of mean differences

Can someone explain in detail how $z_\text{total}=z_{\alpha} + z_{1-\beta}$ in a one-tailed hypothesis test of mean difference $\mu_1 - \mu_2$ with common variance in order to determine sample size. ...
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Sample size calculation for hypergeometric distribution with skewed (very low or very high) proportion

I have hypergeometric distribution with: population size N = 500, population proportion = 0.01 (1%). This is estimated proportion from previous experiments. I need to calculate sample size, to verify ...
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Power calculation with a binary outcome (using a R package & manual simulation)

I am trying to compare three different methods for power calculation under the same setting. Although I understand that the power estimates from each method cannot be exactly identical due to ...
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Likert scale and sample size

I want to study the satisfaction of a mother receiving paper or website information. I will have at least 5 questions, with Likert scale (5 points) each time. For the sample size: Should I calculate ...
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Updating population variance assumption after sampling

I'm trying to get my head around how to think about a situation where an assumption on the population variance in the sample sizing stage of an experiment goes wrong. Let's say I'm estimating a ...
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Choose sample size in Linear mixed models. Ethical considerations

There are no reference articles on this topic, the linear mixed model requires real data on results to calculate the sample size, unlike an anova model that requires data on power, significance and ...
62 views

Sample size. Paired T-Test and repeatability

The study involves 10 subjects, in which we measure speed with 4 different shoes, and the measurements are repeated 4 times, and this is done on two different tracks, indoor and outdoor. On the one ...
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Sample size calculation for Cox regression for comparison of four treatment groups

I need to calculate the required sample size for a future study. We have 4 treatment groups, one of those will be the control group. The goal is to compare each of the 3 treatment groups to the ...
1 vote
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Sample size for Survival Analysis (Cox regression) with discrete time

I have a study where the patients come to the hospital every two months for check-ups. T0 ( one week before surgery), T1 (two months after surgery), T2 (4 months after surgery) up to T9 (18 months ...
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Sample size for a vector of proportions and simulation

Currently, there are more than 10 variants of omicron virus. Say, variant proportions are X1=0.1, X2=0.35, X3=0.15, etc. I need to calculate the number of samples needed to detect the proportion of ...
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Can I compare means and demographics (categorical) between my small sample of 45 respondents to a national sample of about 40,000?

I have a sample of 44 participants who answered the same questions as a national sample of about 33,000 participants. I have the full data set of the national sample. I would like to compare means on ...
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Sample size for survey

My interest is to perform a statistically significant survey on a population of 1700 people, that can be described in different categories, so each person belongs to only one category. I have two ...
188 views

Calculating sample size for comparing pretest and post-test scores

I am trying to evaluate a new curriculum. I intend to do it by giving students a test at the beginning of the academic year (pretest) and one at the end of the year (post test). There are roughly 50,...
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The multivariate DKW inequality is given by $$\Pr \left[ \sup_{t \in \mathbb{R}^k} \left| F_n(t) - F(t) \right| > \epsilon \right] \leq (n+1)k e^{-2n\epsilon^2},$$ where $F_n(t)$ is the eCDF, $F(t)... • 9,229 2 votes 1 answer 114 views Multinomial logistic regression sample size I'm an undergrad student completing my dissertation research proposal. I am trying to calculate a sample size for my multinomial logistic regression analysis. The criterion variable is degree type ... • 21 4 votes 2 answers 200 views sample size calculation using G*Power -- which model to use based on an already calculated effect size? I want to perform a sample size calculation using G*Power. I have 2 predictors and want to test how these 2 predictors affect change over time in a specific cognitive measure. The cognitive measure ... 1 vote 0 answers 22 views Sample size calculation for prevalence studies: how do I find d when reviewing a published study? I have found the following formula in Munn et al.: $$N = \frac{Z^2 P(1-P)}{d^2}$$$N$= sample size$Z$= statistic for a level of confidence$P$= expected prevalence$d$= precision The problem I ... 0 votes 0 answers 46 views Second Generation P-values in the Context of Statistical Evidence and Sample Size I am currently doing research on statistical analysis, and I have come across the concepts of Second Generation P-values (SGPVs) introduced by Blume et al. I understand that these are used to ... 1 vote 1 answer 28 views How do I determine sample size for determining a trend over time? I want to characterize how batteries degrade over time. Due to the chemicals within the batteries, they naturally decay, resulting in batteries having less energy over the years. I want to figure out ... 4 votes 1 answer 116 views Sample size calculation for proportional odds model Apologies in advance for my lack of statistical knowledge/insight! I am trying to calculate the sample size for a clinical trial of treatment A versus placebo with primary outcome of prolongation of ... 0 votes 0 answers 13 views Estimate subgroup sizes with a a given OR including CI and total sample sizes We are doing a meta-analysis using OR as the effect size, but on a limited number of trials. The data is a bit messy and some numbers are missing - at least for our purposes. I was wondering if there ... 0 votes 0 answers 49 views Sample size calculation within-subject I need to conduct a sample size analysis for an experiment with the following characteristics: One intra-subject independent variable is the type of cheese with two levels, Cheese A (1) and Cheese B (... • 1 0 votes 0 answers 29 views Calculating Sample Size for Cumulative Link Mixed Model (CLMM) I am going to collect data in which each participant answers to 3 questions to 18 vignettes (each vignette has 3 questions), each question with likert scales 1-5. The dependent variables (questions) ... 4 votes 1 answer 270 views Small Sample size I have collected primary data from 100 tech startups. However, there are 23k active tech startups. Given that, how will I justify the small sample size. I am collecting the data from an emerging ... • 65 0 votes 0 answers 48 views Required sample size for logistic regression? Early stage PhD candidate trying to suss out project specifics. Currently trying to calculate the sample size required for a binomial logistic regression with one IV and one DV, alpha level 0.05 and ... 0 votes 1 answer 17 views Relative importance of equal sample size vs equal sample density I am conducting a vegetation study of the effects of prescribed fire. I have an experimental area that will be burned and a control area that will not be burned. The experimental area has three types ... • 123 2 votes 2 answers 66 views I have a population size of 500 and want to test X number of samples with high probability that I will catch a failure, how many samples do I test? I cannot test all 500 subjects for failure. I need to know how many subjects out of the 500 I need to test in order to understand all subjects outcomes with confidence. What would the formula be? • 21 4 votes 3 answers 142 views Sample size calculation for a multicenter RCT I'm very new to the world of statistics, so sorry in advance for my limited knowledge. I hope you don't mind helping me. We are currently setting up a multicenter RCT of treatment A versus placebo in ... 2 votes 3 answers 71 views Does sample size affect the value of median? I have two groups of A and B. Group A consists of 11 people and group B of 35 people. The results of one behavioral outcome measure is higher for the group B while logically it should be the other way ... • 41 7 votes 1 answer 273 views What sample size should be reported when using pairwise deletion approach with WLSMV? I have a question regarding reporting the sample size in an article. The situation is a bit complex, so please allow me to explain below: I collected data from participants via an online survey. ... • 141 0 votes 0 answers 11 views How can I calculate the sample size in this multivariate problem? I have two data sets containing scores of a test applied to two groups of people: A control group (neurotypical individuals) and a group of people with a specific neurological condition. The aim is to ... 2 votes 1 answer 26 views Regression with depended predictors, animal study sample size [closed] I have a few questions for help, One of my predictors is for treatment and control. Another predictor is dosage. Treatment group has 4 dose levels which control group only has one. Can I still use ... • 191 11 votes 5 answers 979 views Is it possible to calculate the power for a specific beta coefficient in a multiple linear regression? I want to conduct a multiple linear regression where I am only interested in interpreting one beta coefficient but I will adjust for two additional covariates (i.e. three variables total). Is it ... • 211 1 vote 1 answer 73 views Small sample in categorical explanatory variable vs overall sample size In a statistical model e.g. regression, we have to ensure the sample size is sufficient to estimate a given number of parameters. Rules of thumb e.g. n=10 per parameter, or a power analysis, will ... • 819 0 votes 0 answers 18 views How should I approach calculating sample size for number of raters required for a study? I am proposing a study for evaluating reports generated by 3 human experts vs 3 different LLMs on a set of 10 situations. Basically, we're trying to whether the human experts are better or if the LLMs ... 0 votes 1 answer 40 views Relationship between p-value and Cramer's V Is there a relationship between p-value and Cramer's V value after conducting Chi-square test for independence... is for Cramer's V value of about 0.13 the associated p-value is of about 0.001 or it ... 0 votes 0 answers 44 views Sample size calculation for correlated eye data What formula or software package can be used for sample size caculations for correlated eye data? An observational study is being conducted in which participants that have two normal eyes and ... • 467 0 votes 1 answer 55 views Sample size issue I have conducted a questionnaire survey of 20 questions, each question of one answer selection, but only one question is a multiple choice question. The sample size was 1000, means 1000 participants ... 0 votes 0 answers 91 views Is Federer Formula of sample size in experimentation study (t-1)(n-1) ≥ 15 legit? I've seen this formula for sample size determination in experimental studies, which was claimed by Walter Federer, is well-known among Indonesian bio researchers. The formula is:$$(t-1)(n-1) \geq 15$...
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Be gentle, I'm learning here. I have a fairly simple adaptive lasso regression that I'm trying to test for a minimum sample size. I used cross-validated mean squared error as the "score" of ...
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Event studies: does test power depend on the window length?

I am reading Cambell, Lo & MacKinlay "The Econometrics of Financial Markets" (1996). Chapter 4 covers event studies. Section 4.6 provides power analysis of tests discussed in section 4.4....
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Validity of R pwr package for extremely small sample sizes (<10)

Edit: this question is not: about programming About post-hoc power analysis (at least not with the intent to use sample statistics in post-hoc analysis - I have pretty good population estimates and I ...
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Why sample size calculation for RCT almost always uses simple univariate test?

I noticed that most RCTs use simple univariate statistical test to perform sample size calculation. For example for continous outcome, z-test may be used. But eventually for final analysis, mixed ...
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Small-sample binary logit and linear models - response to referees [closed]

Background: This is a cross-sectional study that collected 30 thrombosis samples. We assessed the presence or absence of MP components (dependent variable), with 24 cases having MP (1) and 6 cases ...
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Sample Size impact on Effect size

I have a small sample size ($n = 23$) and I ran some t-tests to see if there were any group differences (group one had $11$ participants and group two had $12$ participants). I can wrap my head around ...
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How to estimate the sample needed to train the binary classification model?

Let's say the population is 100 thousand, the share of the target variable is 1%. I found calculators that, based on the normal distribution, find to confirm a share of 1% and give an estimate of the ...
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Choosing a suitable sample size for a Random Forest Model

I know that this isn't always a straight forward question to answer, but I am working on a provincial wide wetland classification model that has $7$ classes and $32$ or so explanatory variables. In my ...