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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Logistic Regression: What do people exactly mean by “cell size”? (example: small cell N's but no warning messages and convergence criteria met.)

I've been performing some logistic regressions and found some great results. The problem is I'm unsure if my model is stable or not. This is mostly because I am confused about what people mean by ...
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0answers
10 views

Is there a relation between sufficient statistic and sufficiently large sample size?

I am wondering whether there is a relation between these two terms.
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0answers
14 views

Sample size for testing an output distribution

Please excuse the lack proper mathmatical notation. This is mostly from intuition about the underlying logic. Given a function $f(x)\rightarrow$ A or B randomly The function should return a ...
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0answers
6 views

Question on how to setup the variables and study

Background: I work in a health care company that use phone calls to remind members for their insurance renewal. I want to find out what is the relationship of (number of phone calls vs. outcome), ...
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0answers
17 views

Sample size references

For calculating sample size in clinical research, I have encountered different ways. For example, using lognormal distributions or calculating using ICC. I am confused which method to apply. Could ...
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1answer
12 views

Does sample size include respondents?

If there's a given population X, and I chose to send out surveys to Y amount of people, but only Z amount of people respond - Would the sample size be Y, or Z? Survey Monkey states that the sample ...
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1answer
27 views

Sample Size vs Iterations (CLT)

I am slightly confused by the term 'sampling size'. Let's say we have N-dimensional distribution and we take one sample (i.e., one vector of N-elements) and measure it's mean. Now let's do 100 ...
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1answer
47 views

Method to test whether a small number of perfect correlations can be trusted within a large sample

There are two binary vectors with 0s or 1s as values and the correlation between them is calculated; this is done for 20,000 pairs of vectors. Theoretically, is there a difference between having only ...
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0answers
18 views

Determining sample size using power analysis in multiple testing context

I am currently trying to determine the required sample size for an experiment. As I want to use the statistical power concept (for a t-test) to determine the required sample size, I want to specify a ...
1
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1answer
30 views

Does increasing sample size have any effect on omitted variable bias?

Say I have a multiple linear regression model, where two of the variables are positively correlated, and I omit one of these variables from the model. First question - if I increase the sample size, ...
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0answers
12 views

sample size for multi-arm randomised control trial measured over time

I would really appreciate any advice on calculating a sample size: This study involves looking at a specific disease, then performing a randomised control trial in two different geographical areas ...
0
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0answers
16 views

Sample size for 99% confidence — Twitter user locations

I'm working on a fun project, trying to understand where people who want to vote for Donald Trump live. Basically I'm on Twitter pulling in public data (location and tweets) on users who mention ...
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0answers
9 views

Power calculation - categorised continuous exposure in case-control study

I have a continuous exposure that I would like to catagorise it into quantiles according to the distribution of control (i.e. 25% controls in each exposure level group). From pilot study, I know that ...
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1answer
10 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 ...
0
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1answer
24 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 ...
1
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1answer
32 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
15 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 ...
0
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0answers
14 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
22 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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42 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
17 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 ...
1
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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
19 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
131 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 ...
0
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0answers
15 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
12 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
19 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
73 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 ...
0
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0answers
31 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
43 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 ...
0
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0answers
10 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 ...
0
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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
20 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
27 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
18 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
63 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
38 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
38 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
14 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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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 ...
0
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0answers
17 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
402 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 ...
0
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0answers
14 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
185 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 ...
0
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0answers
17 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 ...
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1answer
76 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 ...