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
19 views

Standard deviation of sample mean - unknown equation answered

Does anyone recognize mathematically or statistically what this formula's purpose is. If it is not statistically useful what does dividing a value by a constant and taking a square root mean? For ...
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0answers
11 views

Jeffreys Interval Calculations and Sample Size

I have a rough understanding of bayesian statistics and of the Jeffrey's Interval/priors. I understand that the Jeffrey's interval takes the form: $$p\mid x \sim \mathrm{Beta}(x + 0.5, n - x + 0.5)$$ ...
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0answers
11 views

Sample size determination for estimating a count

I want to estimate a simple variable: "**how many times my website is visited in 2015?". Suppose that I cannot count all visits to my website (it is expensive!), but I can count the connections on ...
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0answers
10 views

Sample Size Calculation Using Wilson Score

I am using a number of different sample size methods to compare their usefulness for a particular study. One of these is the Wilson Score Method. I am searching for a table or chart of the sample size ...
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0answers
26 views

Correlation analysis with simulation

I need to determine if two variables are correlated (have a relationship between each other). Issue 1: both variables take on values greater than O, in which, I can not assume normally distributed. ...
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0answers
4 views

sample size for longitudinal quasi-experimental evaluation

I am working on the evaluation of a proyect designed to help crime victims to overcome their experiences. My main hypothesis is that the program prevent these victims being crime victims again. Since ...
2
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1answer
52 views

Why would you want a smaller critical region when testing large samples?

Is it because when you have a smaller critical region you have a smaller probability of the event happening?
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0answers
9 views

Calculating sample size for two-way ANOVA given effect size

I have an experiment with two groups and three timepoints (different subjects for each timepoint, so no repeated measures), and I understand a two-way ANOVA would apply to this situation. I'm trying ...
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0answers
12 views

From successive samples of increasing size how do I measure “variability is within the error band” for a particular confidence level?

In the section 5.6 of book Data Preparation for Data Mining, by Dorian Pyle it states This is a complex subject, and it is easy to confuse what actually has been captured here. In the example ...
1
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1answer
23 views

Sample size calculation

Medical student doing his first research here. This is a randomized controlled trial. Basically the study compares the effectiveness of skin glue over skin sutures. Since the length of each scar will ...
1
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0answers
24 views

Determening sample size n given probability type 2 error

Given population, which is normal distributed with $\sigma = 4$ , the Z-test must be done with $H_0$: $\mu = 10$ and $H_A$: $\mu$ $\ne$ $10$ with significance level $\alpha = 0.05$ Is sample size $n=...
1
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1answer
30 views

Multilevel modeling sample size

I have a question regarding multilevel modeling. I am building a 3-level model: 1st level yearly observations (variables which vary between years), 2nd level variables on company level, which do not ...
0
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1answer
19 views

What is my sample size?

I'm a cell biologist. I have a seemingly easy question for which I've received opposing answers. I'm trying to compare the number of peroxisomes (a cellular organelle) in control cells and those ...
0
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0answers
7 views

How to test if the difference between two logit-function-fits is significant or not?

I am considering a binomial experiment where each trial can only have two possible outputs (0,1). I vary the value of a predictor (experiment parameter) and repeat the experiment several times for ...
3
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0answers
20 views

How to check the assumptions behind an inference procedure, in the case of very large data sets

On this site it has been confirmed multiple times that, contrary to what is often heard, hypothesis tests don't have any issues with large sample sizes. As a matter of fact, the probability of Type 1 ...
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0answers
9 views

Blocking and representative samples

I am trying to measure the Net Promoter Score of a segment of customers for an online product. There is an attribute of these customers that I believe might affect their Net Promoter Score. So I want ...
1
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2answers
34 views

Significance level in sample size calculation and in final analysis

Imagine that for the purpose of a study a sample size is computed with the following formula for a given power $1-\beta$, difference in means $\epsilon$, standard deviation $\sigma$ and significance ...
2
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0answers
108 views

Small sample size - repeated measure ANOVA or something more simple?

I have data from an ecological study on wasp abundance and diversity across a forest which I am trying to analyse appropriately. We have abundance data from ten locations that were sampled twice, ...
3
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0answers
42 views

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
12 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.
0
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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
8 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
26 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 ...
0
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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 ...
1
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1answer
31 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 ...
1
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1answer
49 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
23 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
35 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, ...
0
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0answers
16 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
17 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 @...
0
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0answers
15 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 ...
0
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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
36 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
24 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
18 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 ...
2
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0answers
47 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 ...
0
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0answers
20 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
19 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
20 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 ...
0
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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 ...
1
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3answers
157 views

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

Let $X$ be a $n \times p$ matrix ($n \geq p$ like a conventional data matrix), with each column j filled by iid draws from a variable $\mathcal{X}_j$. I would like ...
0
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0answers
18 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.
1
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0answers
23 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
74 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
41 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? I can't find any ...
0
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0answers
59 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
12 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 ...
0
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0answers
14 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 ...