This tag is very ambiguous. Use it when the question is about sample size & the following are NOT more appropriate: [small-sample], [large-data], [power-analysis], [power], or [underdetermined].

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1answer
9 views

Sample size - prioritizing issues

Hi I am about to distribute a survey that asks stakeholders to pick from a list of 20 issues, the top 3 they feel are important. I am not doing any hypothesis testing but ranking the results based on ...
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1answer
23 views

Can I exceed the estimated sample size?

I'm doing a cross-sectional descriptive study with an estimated sample size being 140. Will it be statistically justifiable if I managed to collect a sample of 200? Could there be any side effect that ...
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1answer
26 views

number of participants to have a 80% chance of detecting a 1.5% point difference as significant

Can someone explain how the math used to determine that 34 participants were required for this study? To have an 80% chance of detecting a 1.5–percentage point between-group A1C difference as ...
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0answers
10 views

Minimum sample size for multiple choice question

I have a question about minimum sample sizes for a multiple choice survey. I have searched around this site and the internet, but haven't found a 100% clear answer yet. What if someone a survey was ...
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0answers
9 views

Best way to calculate power, precision & sample size using complex pilot data set?

I have a large and complex pilot data set of electromyographic (EMG) data collected from human subjects performing several different exercises. A single subject was used for all data collection in ...
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0answers
21 views

Determining the required sample size to meet a bound

A company produces a special kind of utility terminals. It has N = 26016 such terminals out in the field in some city for many years. Over time these utility terminals go bad. The company decides to ...
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0answers
38 views

What is my study design

I have two sample groups and I will not be manipulating the participants in any way so this is not an experimental design. However I wish to compare the results of the two samples (between subject ...
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0answers
14 views

GLM required sample size

I'm doing 2 different types of generalized linear models. A Poisson GLM for claim counts and a Gamma GLM for claim amounts. I've read a lot of literature about GLMs but I still haven't found a ...
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1answer
17 views

What is the proper way to increase power when randomizing at the village level?

Let's say that we have a hypothetical RCT with the following information: --We are interested in seeing whether a particular belief held among some individuals in a developing country can be ...
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0answers
4 views

Simulating thousands of regressions and obtaining p-values [migrated]

I'm looking to do some basic simulation in R to examine the nature of p-values. My goal is to see whether large sample sizes trend towards small p-values. My thought is to generate random vectors of ...
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0answers
19 views

Sampling size question [closed]

I wanted to know the sampling size of a population where size is low and moreover it doesn't follow a normal curve. Moreover I wanted to roll out quality numbers at monthly level as the weekly level ...
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0answers
18 views

Reverse solve chi-squre statistic to find number of observations

I am trying to prove that two proportions are equal with 95% confidence. I have a total population Tp (10000), and wins in that population of Wp (2000). My sample size is Ts (1500). I need to solve ...
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3answers
126 views

Decrease of $(X'X)^{-1}$ as n increases

Let $X$ be a $n \times p$ matrix, filled with iid draws, with $n \geq p$ (like a conventional data matrix). I would like to show that, in a sloppy notation, $(X'X)^{-1} \rightarrow 0$ as $n ...
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0answers
13 views

Sample size for correlation study if r=0.39?

I am doing a correlation study. I need help in computing the sample size given the correlation coefficient of 0.39 with a power of 0.80 and alpha of 0.05? Thank you and hoping for answers.
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0answers
11 views

Diffrence in required sample size for estimating a trend with GEE in longitudinal Data

I am currently working on GEE's for longitudinal data and the model I am using to simulate and evaluate the data is: $y_{ijk}=\beta_1+\beta_2\cdot j+\beta_3\cdot k+\beta_4 \cdot j \cdot ...
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0answers
15 views

Multiple imputation: How many subjects per variable are needed?

I want to perform a multiple imputation via the mice package in R. My dataset looks as follows: 250 observations 60 variables variable type: numeric approximately 7-10% missings per variable ...
2
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1answer
70 views

Sample size choice with binary outcome

Our civic association is planning to implement a survey asking our neighborhood one true false question. I would like to make sure that we obtain an adequate sample size. Let's assume N = 2500 ...
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0answers
30 views

Population Proportion Confidence Interval

Looking at the equations for confidence interval and sample size estimation of population proportion, I don't understand why population size isn't a factor. Can anyone explain? Thanks! $$ \hat{p} \pm ...
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0answers
29 views

sample size to estimate mean of zero modified log normal variable

I would like to estimate the average value of a variable "A" in a population. I think only 5% of the population has a figure of A > 0, 95% has A = 0. Using a previous non random sample, I believe the ...
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0answers
8 views

Does Sample Size Affect Partial Eta Squared values when running a Mancova or Ancova?

I am currently running an ANCOVA and MANCOVA for my research and need some help in terms of understanding the Partial Eta Squared(PES) values given to me off on SPSS. I am first wondering if with PES ...
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0answers
8 views

Survey sample size

I am trying to learn something about survey design and analyisis and I have a doubt about the number of people that should answer a multipurpose survey in order to estimate several proportions. If a ...
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0answers
3 views

Minimum n for category in multinomial logit

I am trying to run a multinomial logit in which my dependent variable is ethnic self id. The variable has 5 categories that are just nominal, and the smallest category has 50 respondents, which is ...
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0answers
19 views

Sample size needed for Gaussian process classification

I recently read the paper by Loeppky et al. on Choosing the sample size of a computer experiment: a practical guide and was curious to know if there were rules of thumb about the sample size ...
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1answer
25 views

Compare several means with different sample sizes (greater than 2)

I have seven different groups with different sample sizes and variances and I want to compare the means of their data. I'm not very informed in statistics, so could anyone help me out here? I've only ...
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0answers
16 views

What is the sample size in this experiment?

We have to determine the sample size in the following experiment. We are trying to determine the concentration in which a combination of drugs works the best against cancer cells. This involved cell ...
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1answer
62 views

Sample Size and Sensitivity/Specificity [closed]

1,765 patients were given a positive/negative screening test for a disease. N = 415 patients tested positive N = 1,350 patients tested negative Due to constraints, not all 1,765 patients were given ...
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1answer
35 views

relationship between sample size requirement and resulting p value

If one uses a web-based sample size calculator for a chi square analysis, the resulting sample size seems to have little relationship to the sample size required to obtain significance, eg. .05. For ...
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0answers
32 views

Best sample size formula and continuity correction for tiny proportions?

I have found the following formulae (from http://www.itl.nist.gov/div898/handbook/prc/section2/prc242.htm) to estimate the sample size required to test the binomial proportion in a single sample. I ...
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0answers
12 views

Sample size calculation for weighted Kappa

I will highly appreciate if anyone let me know how to calculate sample size for weighted kappa. I do know how to do it for unweighted kappa.
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0answers
22 views

Sample size to test small proportion

What sample size $n$ is required to test the following binomial probability in a single sample: $H_0: p \leq p_0$ $H_1: p > p_0$ Is there an exact, robust formula to calculate $n$ in terms of ...
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0answers
16 views

reusing previously generated random samples

Suppose, I wish to generate random samples from normal distribution $\mathcal{N}(\mu, \sigma^2)$. I already have a normrand() function. Technique 1 Each time a ...
2
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1answer
373 views

How to find correlations between multiple low-frequency variables?

Let's say we have multiple ($k > 2$) binary variables (e.g., genetic mutations and/or disease states), which appear at a given frequency of $f(1)$ to $f(k)$ in a sample. We would like to test ...
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0answers
13 views

Sample Size and Margin of Error

I'm crafting a study and am not sure if the below hypothetical approach is right: A robotic eye scans man made machine parts for defects. 500 machine parts were made in Feb 2016. A human inspector ...
3
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2answers
176 views

Why do small sample sizes give more significant p-values for rare events?

Maybe I'm getting a bit confused, but I have a single binomial variable with very low frequency (e.g. 1 event in 100,000 trials), and I'm trying to figure out what sample size is required to show a ...
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0answers
16 views

Likelihood based on sample mean from Gaussian

If we know that mean of sample is 4, and that sample size is 3, and that samples are taken from Gaussian distribution with variance 1, i.e. N(u, 1), what can we tell about distribution's mean?
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0answers
15 views

Multiple mediators, sample size

I wonder if anybody can help me to get the right answer to a question about mediation (using Process). I want to test if Difficulties in Emotion Regulation (DERS) is a mediator between other 2 ...
4
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1answer
73 views

Adjusting for variance-sample size dependence

In many survey results that are released to the public with respect to ranking (whether it be school ranking, city crime rates, etc.), one of the many criticisms of these is that some which have small ...
2
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1answer
34 views

Some questions on multiple logistic regression

Let's say we have k binary (binomial) variables, and a sample size of n observations per variable, where each variable occurs (positive case) at a given frequency/probability f. We would like to check ...
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2answers
54 views

Number of Markov chain Monte Carlo Samples

There is a lot of literature out there about Markov chain Monte Carlo (MCMC) convergence diagnostics, including the most popular Gelman-Rubin diagnostic. However, all of these assess the convergence ...
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0answers
14 views

Find sample size representative of data

I have data from multiple farms, showing how many healthy and lame animals are found on each farm, and how many animals were there in total. I would like to calculate, statistically, how many animals ...
1
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1answer
79 views

Wilcoxon test for sample n=3

I have a dataset of male and female bats. Male bats comprise 3 evening and 3 morning trips. Female bats 5 evening and 3 morning trips. Trips consist of parameters like trip duration, covered ...
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1answer
21 views

What should be the ratio between number of cases and attributes in multivariate regression?

Is there any way to determine if it is feasible to perform a multivariate regression based on a given number of samples and attributes? For example I have a data set with 6 cases , 30 attributes and ...
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0answers
20 views

Solution for small sample size for logistic model [duplicate]

My friend asked me today about how to deal with the problem with small sample size for a logistic modeling project. Let's say that she has a sample size of 100 obs and she would like to have a sample ...
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0answers
7 views

How can I construct species area curves with samples of different sizes?

I’ve got a data frame with 5365 rows (plant sociological relevés) and 1035 columns (species) and would like to set up smoothed (i.e. randomized) species against area curves (SAC). The problem is that ...
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0answers
45 views

Calculate sample size (DeMoivre-Laplace)

I have difficulties with calculating sample size. In the task the question is what sample size is needed to prove whether CTR changes or not. There is a banner with CTR = 1,5 % Also there is a new ...
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0answers
7 views

Choosing a Size of Reference Population to Assess Variance that is Statistically Significant

Consider this scenario. I have a sample (Sample A) of independent data with 1-10 measures on an attribute (fat score). Fat Score of Sample A: {2,5,6,7,7,6} I have an option of choosing a ...
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0answers
18 views

Effect of reliability on sample size

I asked a similar question here: Meta-analysis using experimental reliability data However as I did not get any feedback (probably for a good reason, which I would like to understand) I ask the ...
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0answers
28 views

Estimate sample size for power-law-ish distribution with cutoff

I'm running Monte Carlo-simulations of a physical problem, where each simulation produces a single number, and I would like to estimate what sample size I should use in order to be reasonable sure of ...
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0answers
12 views

Effect of number of samples on error in classification/regression

Let's say for a classifier, $E_{out}$ is the test error and $E_{in}$ is the training error, $N_{out}$ is the no. of test samples and $N_{in}$ is the number of training samples. I want to know the ...
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0answers
24 views

Is it possible to compare unequal sample sizes in a non-parametric paired t-test?

I'm trying to compare counts of species made during the day and during the night. The counts were made in the same location for day and night and were on the same populations. Therefore, I'm assuming ...