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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43 views

What statistical test would I use to test that both data sources are matching [on hold]

Suppose I am only working with two datasets, Data Source 1 with columns Customer ID and ...
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15 views

Effect sizes - N or n? [closed]

This may be a stupid question but do you calculate an effect size using the full sample size (N) or can you calculate using the number of subjects in each level of the independent variable (n)?
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30 views

Sample Size for Case-Control Study

We wanted to perform a case-control study and used the calculation below. Using alpha = 0.05, beta = 0.20, p1-p2 = 0.003, and a ratio of controls to cases of 1000:1, we came up with a sample size of ...
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10 views

How do I calculate sample sizes for multiple proportions, while maintaining a certain ratio of the sample sizes?

I am trying to perform z-tests for multiple proportions, while maintaining a certain ratio of the samples. For example, let's say I'm trying to compare 3 populations, and I want to maintain the ...
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1answer
15 views

Does random sampling from a dataset produce the same distribution as the original space?

Let's say we have a dataset $D$ with $N$ rows and $M$ columns. Each column is a feature. And for each feature $X_1, X_2,..., X_N $~ iid $F_p$ where $F_p$ is the distribution for feature p. Now let's ...
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27 views

Split dataset per rows into smaller files in R [migrated]

I am analyzing a dataset, with 1.14 GB (1,232,705,653 bytes). When reading the data in R: trade = read.csv("commodity_trade_statistics_data.csv") One can see ...
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23 views

How do I do a power analysis for a fractional factorial design?

I want to do a power analysis for my 3x2x2 design, but I am not using the full factorial design, but rather a fractional one, so instead of using the full 12 groups, I actually only have 6. I was ...
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71 views

What is Bayesians' equivalence of sample size determination? [duplicate]

Under the frequentist framework, one can use power analysis to determine sample size for a given effect size, significance level, and power. How are similar questions answered under Bayesian framework?...
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20 views

Estimating a sample size $n$ such that $\mu' n < y$

It seems like a pretty standard statistics question, but I couldn't find the answer. I have a sample from a population, from which I can estimate $\mu$ the population mean. I don't know the real ...
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14 views

What is the procedure for conducting a power analysis for regressions with clustered standard errors?

I am wanting to carry out an OLS regression with 5 predictor variables across 10 traits, with each row in my data consisting of a combination of participant and trait, so each participant will have 10 ...
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17 views

Probability: Estimating Database Size with N Smallest Random Values

Note: This was first posted on StackOverflow, but I did not have much luck there. I have a very large database. Each item in the database is assigned a uniformly distributed random value $\geq 0$ and ...
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1answer
23 views

Correcting for bias in GEE models with small cluster size

In GEE, several methods have been proposed for correcting for bias when the cluster size is small to moderate (<40). Some have proposed alternative variance estimators, e.g. Morel, Bokossa, and ...
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2answers
12 views

What A/B test calculator can I use to calculate the minimum same size for uneven split between control and treatment groups?

I have only come across A/B test calculators that give the minimum sample size per variation for 50-50 split between control and treatment. I am running an A/B test for conversion rates with a 80/20 ...
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1answer
61 views

Minimum sample size for Spearman's correlation and Kendall's Tau b

I've tried looking for scholarly articles to determine the minimum sample size that is required to perform either the Spearman's correlation and Kendall's Tau b hypothesis tests. However, I can't seem ...
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1answer
23 views

Expected value of CDF evaluated at sample min/max, with respect to sample size

I've been using simulation to investigate the behavior of cumulative density function evaluated at extreme values of a sample. Functionally, my study has $n$ instrumented fish migrating downstream ...
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2answers
41 views

How to deal with drastically different sample sizes (3 treatments)

I have 3 treatments with different sample sizes. They are different enzymes for production of Butanol in industrial scale. The first one has 60 replicates, the second has 30 replicates and the thrid ...
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37 views

2x3 design, binary out come sample size calculation?

I'm designing an experiment as part of a marketing assignment. I'm planning on running a 2*3 between-subjects design (6 conditions comprised of two factors, one with 2 levels and one with 3 levels). ...
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1answer
24 views

Unequal Sample Size, Similar Variance

I'm comparing an intervention using a pre and post knowledge survey. My pre sample size is n=37, my post is n=32. The variance for the pre is 7.08 and 6.94 for post. The histogram of the pre is skewed ...
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5 views

about the sample size calculation of three or four groups in survival analysis

I have a question about the sample size calculation of three or four groups in survival analysis. Do you know some package in R, Stata, or other resources?
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9 views

Calculating test group sizes for Statistical Significance in Subject Line split Testing

Hoping for some insight or advise on the calculating ideal test group sizes in this the following scenario: Say I have a million contacts that are delivered an email campaign I want to implement a ...
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0answers
21 views

Pairwise comparisons pre test post follow up

I have to complete my dissertation in a couple of days. I am proposing a RCT with two independent variables: treatment( group 1 : avatar cognitive therapy , group 2: CT) and time(pre-test, post-test ...
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1answer
26 views

Sample size prediction in multivariate A-B testing

I need to run an A-B testing with one control group (40%) and 3 variants (20%) each. Base line = 0.65 Target lift = 0.25 Power =0.8 Confidence = 95% I found following R code to find minimum ...
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2answers
33 views

Zonal statistics (mean± StDev) from polygons with different area

I am analyzing a temperature image using a land cover map with the overall goal to prepare a barplot where I report the mean ± StDev temperature for each land cover class. To do so I assigned each ...
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Implications of adding extra “control” conditions to an ANOVA?

I'm planning a 2x3 ANOVA, all between subjects. I'm expecting a weak main effect for A...a main effect for B where one condition is different than the other two...and then an interaction effect where ...
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12 views

Using power and significance to calculate sample size in a one-tailed test?

I am trying to determine the sample size needed to demonstrate that the lower boundary of a 95% CI is not lower than the population mean of another, with a power of .9. Right now the formula I'm using ...
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1answer
19 views

Sample size calculation for multivariable Cox regression for treatment comparison

I am trying to calculate the required sample size for a future study. Specifically, the goal is to compare two treatments based on their survival. The Cox model will be used, and along with the ...
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0answers
8 views

Minimal number of obs for BEKK(1,1) and DCC GARCH

For my thesis I am using a rolling regression to estimate the BEKK(1,1) and DCC GARCH parameters and their corresponding confidence intervals. There is literature on the minimal number of ...
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33 views

Stats questions for a laboratory experiment with a small number of animals

I've been asked to run the stats on an animal behaviour experiment performed in a laboratory setting and, coming from a field ecology background, I have some basic questions regarding how I should ...
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1answer
28 views

Have I calculated my estimated sample size correctly?

I am conducting a study to answer the following question: In women with type 1 or type 2 diabetes in pregnancy, is there a difference in glycated hemoglobin A1C level between women who have a high ...
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0answers
20 views

Which effect size to determine sample size in power analysis for mixed effects model?

Experimental design: 3x12 repeated measures. I ran a mixed effects model that revealed an effect of "variable x" for which there are 12 levels. Post-hoc analyses based on this model (paired samples ...
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0answers
11 views

Repeated measures with rotation of subjects within groups

I was wondering if you could help with the interpretation of a potential experimental design. We are testing two versions of a 'group' exam, score (out of 100) being the outcome variable, aggregated ...
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0answers
16 views

Clustering Algorithms- Sample Size

I have a small sample (290 observations) of categorical data and I am trying to decide on what clustering method to use. I am considering k-medoids, hierarchical clustering and Latent Class Clustering....
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1answer
36 views

How to determine the sample size for variance calculation in AB testing?

I am studying AB testing. I can understand that the sample size for AB testing would require the variance information. And many online calculators can provide sample size for each group in AB testing. ...
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0answers
12 views

Large population size = relatively smaller sample size?

Assuming 95% Confidence Level & 8% Margin of Error, a population frame of 37 yields a sample size of 30 (81% of pop) but a population frame of 370 yields a sample size of 107 (29% of pop) and a ...
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0answers
11 views

sample size to detect variability in a sample

I have a sample of continuous data which I use to build a random forest model. Now I want to determine, how many additional samples I would need to improve the prediction (reduce the RMSE by a certain ...
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1answer
23 views

Calculating Sample Size As Number of Days Needed For Significance?

I am trying to determine required number of days required to reach a significant result for a one-tailed independent sample test. I have sales data by day for my test and control group. The results ...
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0answers
14 views

Power of Tests for Proportions: One Proportion vs. Two Proportions

I am trying to calculate the required sample size for a trial, where my outcome is proportions (for each subject I am measuring if the subject had an event or not). I tried two ways and got different ...
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0answers
16 views

Testing if number of observations in experimental conditions is statisically different

I was conducting in experiment in which i sold products on a pay-what-you-want basis in 4 different information conditions. Apart from comparing the average willingness to pay across the 4 different ...
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0answers
24 views

How to compromise between using a lagged dependent variable and observation loss

I am working with panel data of several thousand observations in five time periods. As I have a strong reason to believe that past values of the dependent variable (DV) affect subsequent values of the ...
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1answer
19 views

Sample size for proportions and fisher exact test

I need some clarification. I am doing a chart review. Plan to test significance with fisher exact as its two interventions, one yes/no outcome. Presumed prevalence in the population is 15%, but ...
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2answers
33 views

What exactly is the sample size of an investigation?

My understanding of sample size is that it is a portion of the population that serves to represent the population. However, I'm not sure if the sample size of an investigation to investigate how X ...
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1answer
23 views

What is the sample size formula which i could possibly get minimum value in-vivo studies?

I am an undergraduate students who is struggling on how to do in vivo studies with my low budget. Therefore, I ask some help of you just in case you know about what sample size formula that I could ...
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1answer
25 views

Sample Size Experiment Proportion Failure

I have N machines and I want to implement an experiment E in them in order to improve their proportion of failures. However, I’m not sure yet if this experiment E will increase, decrease or do ...
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11 views

Sample Size Proportion Comparison Test Finite Population

How can I calculate sample sizes for a Prorportion Comparison Teste of Finite Populations? Is there a function in R? Basically, I want to know what is the finite population version formula for the ...
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0answers
16 views

Sample size calculation and number of independent variables for repeated measures Generalized Estimating Equations

I'm trying to understand sample size estimates for repeated measures Generalized Estimating Equations. Reading papers on this topic, it seems that the number of independent variables are not assumed ...
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1answer
18 views

Is survey response number big enough

This is a fictional example to demonstrate my question I'm trying to figure out at work. I sent out surveys to all organizations of a specific type in the US asking them what is the average time it ...
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0answers
13 views

How to infer the distribution of a statistic (Bayesian inference?)

I have a list of approximately 30,000 venues in a major US city. These venues hold all kinds of events, sports, conferences, concerts etc. I want to know the distribution of the 'capacity' of these ...
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1answer
19 views

Resource for an explanation of Sample size calculation when $\alpha$, Power and Effect Size for t-Test are given

For a simple z-Test or t-Test (one-sample or two-independent-sample with $n_1 = n_2$ and equal variance) I want to calculate the required sample size $n$ when the significance level $\alpha$, power ...
0
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1answer
19 views

Do ANOVA & MANOVA require balanced levels?

I have one independent variable with two levels, or categories, and four dependent variables. When doing a MANOVA or ANOVA test, how important is it for the number of observations in each category to ...
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1answer
28 views

sample size calculation in 3-arm survival analysis

In a 3-arms clinical trial, with time to event data, either A is superior to C or B is superior to C it will be considered significant. No need to compare A and B. I know how to calculate the sample ...