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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Alternatives in designing regressions with a factor with many levels

Ok, maybe it wasn't the best title! I have a regression analysis in which I want to asses the effect of a discrete var against a continuous one. The problem is that the factor variable has 21 levels ...
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2answers
28 views

Minimum sample size for 1 way ANOVA?

I have tested a group of participants over various time points and I want to investigate whether mean score on each subsequent time point is significantly different to the mean score at baseline (eg. ...
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7 views

Sample size in the Latin Hypercube simulation to calculate P90, average and P10 and number of variables relation

I am preparing some simulations to determine the P90, average and P10 of a parameter. How many runs do I need to have to get a reliable answer (let's say 5% margin of error and 95% confidence)? It ...
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1answer
39 views

Determining sample size for AB test with proportion greater than one

So I'm pretty sure I'm thinking about this all wrong, but.. I'm trying to run an AB test on a web platform that will increase the total number shares to a social network (incredibly exciting, I know). ...
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1answer
33 views

How do I calculate required Sample Size to get useful confidence interval length for Bernoulli random variables?

I am pulling meta data fields from a population of 100M documents. These meta fields include things like Author Name, Author Location, Keywords, etc. Some documents have all of these meta fields, some ...
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1answer
24 views

How to compare groups with different sizes?

I need to calculate the winner of a PTA membership contest for our local elementary school. There are 15 classes of different sizes (size based on number of students in the class). We need to see ...
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0answers
16 views

Retrospective power analyis of lmer for sample size

I'm an MSc student doing an assignment where I am asked to analyze and write up a report on a dataset on environmental enrichment in zebra finches. Among other things we are being asked to do a ...
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0answers
15 views

What factors influence the point at which a sampling distribution is said to be nearly normally distributed?

What factors influence the point at which a sampling distribution is said to be nearly normally distributed? *Note that the answer I am looking for is not sample size. I am asking what decides how ...
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1answer
37 views

How to go ahead with sample size selection when population is small

I have sent a survey to 92 persons but so far I have received only 40 responses. By using sample size requirement calculation I need 75 responses for the desired criteria ...
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1answer
71 views

Increasing sample size with bootstrap sampling

I'm trying to perform some classification analyses with a relatively small dataset (201 observations, 32 predictors). There are 8 classes in my data with unequal sample sizes ranging from 10 in the ...
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1answer
33 views

Calculating sample size of a mixed ANOVA in R (2 between, 1 within variable)?

I'm searching for a built-in function in R for calculating the required sample size (given certain power, alpha,..) of a mixed ANOVA (2 between, 1 within variable, 2x2x2 design). Does this function ...
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0answers
39 views

Does Hoeffding's inequality apply to sampling from finite populations?

Based on Hoeffding's theorem, one could easily find the minimum number of samples required for the inequality $\Pr \left(|\bar{X} - \mathrm{E} [\bar{X}]| \geq t \right) \leq \delta$ to hold as ...
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24 views

Sampling Size for a large Dataset

I am having a dataset of size upwards of 200 million rows. I have no knowledge of the distribution of this dataset. Would like to perform some analysis on this - like look at the ...
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0answers
11 views

Compute effect size based on simulation using different lists of different length

For my research purpose I wrote a small simulation to compute an empirial p-value based on an input gene list and a reference gene list. The idea is to check for each gene in the input gene list, the ...
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2answers
29 views

Choosing samples of different sizes - considerations?

Let's say I have four populations with the sizes 2451, 2117, 7577, and 1545. Each of these are sets of activity sequences on which I do sequence analysis. Based on this I want to do clustering based ...
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0answers
9 views

Sample size calculation using G*power for a mixed design

I have performed a pilot study in form of a 2x5 mixed design, with 10 participants. The factor with 2 levels was applied as a between subject factor, meaning that only a half of participants were ...
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1answer
26 views

Sample Size Calculation of Pilot Study

I want to calculate the sample size for my pilot study. My subjects will undergo a certain test once taking a substance before the test, once taking a placebo. My goal is to find out if the substance ...
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0answers
8 views

Balance checking in randomized controlled trials with large sample

I have a survey experiment in which the treated group receives a certain prompt that the control group does not. I also have a bunch of demographic variables that I want to check for balance between ...
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0answers
16 views

Upper bound for sampling fraction for CLT to hold

What is the upper bound for the sampling fraction for the Central limit theorem to hold when sampling without replacement? Context The context for my question is that it is regularly argued (see e.g. ...
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1answer
44 views

How to calculate sample size for this study design?

I am trying to find out whether the number of participants I recruited (N=42) so far is sufficient for my study in which: there are two interfaces (say A and B). ALL students in the study will try the ...
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1answer
45 views

The population size does not affect the sample size? [duplicate]

I used the following formula to calculate the sample size. n = (Z2 K p (1-p)) / i2; (k = 2, Z = 1.96, p = expected proportion, i = 0.03) I noticed that the sample size is not related to the population ...
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0answers
40 views

Sample size for logistic regression with categorical independent variables

Trying to find a sample size for logistic regression I found a rule of thumb in http://www.medcalc.org/manual/logistic_regression.php I cite: Sample size considerations. Sample size calculation for ...
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0answers
37 views

Getting Sample size

Annual starting salaries for college graduates with degrees in business administration are generally expected to be between \$35,000 and \$50,000 (Hint: Refer to the last slide of your Chapter 8 ...
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1answer
192 views

Why doesn't the standard deviation represent a normal distribution?

Why doesn't the standard deviation of a sufficiently large sample represent a normal distribution that we can make inferences from? Let me list my thought process, so hopefully someone can highlight ...
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1answer
17 views

problem: a sample size for the assumed effect in the 2 sample proportion test

I would like to calculate a sample size for the 2 sample proportion test when the significance level is assumed (0.05), power is assumed (0.90) and I'd like 2 sample proportion test to detect that ...
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18 views

number of participants/analysis

Hi I am really struggling here any help would be muchly appreciated, please use laymen terms where possible. research question: a comparison of quit rates between 3 smoking cessation treatments. ...
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1answer
59 views

Cohen's d in proportion test

I am calculating the sample size for proportion test. I would like to have significance level =0.05, power = 0.90 and that the effect size is greater that 5%. I would like to have statistically ...
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0answers
17 views

Problem Approach: uncertainty about sample size

I have a time series of events (weekly aggregate date) Each event is information on contracts closed by a sales representatives during working weeks. The goal is to calculate what is the expected ...
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1answer
38 views

Sample size problem

I am looking for a suggestions on how to estimate the sample size in such a problem. There is a group with one usefull treatment (let's say 10 milion people) but one consider if there might be more ...
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1answer
42 views

Linear regression sample size

I have about 80-100 participants and a single dichotomous predictor as fail/pass. My outcome variable is a continuous one and I want to know if my dichotomous predictor predicts the continuous ...
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0answers
57 views

Sample size calculation for non-normal data (possibly lognormal)

I am currently trying to rack my brains to find a solution but I seem to be coming up with nothing. I have water quality data with which I want to get a sample size calculation from for a future ...
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13 views

Optimizing selection from varying sets

On pages of website(s) I have a set of potential messages to choose from and only one or two slots to show them in. (think 'this product is on sale' or 'this product is new'). On each page the set ...
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1answer
106 views

Why is the sampling distribution of variance a chi-squared distribution?

The statement The sampling distribution of the sample variance is a chi-squared distribution with degree of freedom equals to $n-1$, where $n$ is the sample size (given that the random variable of ...
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0answers
12 views

How do I determine sample size to validate a requirement when I have a lot of margin?

I apologize if a similar question has been asked, but my search has yielded no results. I am having some trouble nailing down the correct methodology to use to design an experiment I am working on. ...
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2answers
114 views

Logistic Regression sample size & bootstrapping

The data for this example can be retrieved here so that you can reproduce these estimates. It is the low birth weight dataset- http://www.umass.edu/statdata/statdata/data/ There are 59 1's and 130 ...
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26 views

Calculate Sample Size with VERY small standard deviation

I am facing a problem trying to estimate sample size for an A/B website test I am currently running trying to investigate difference in revenue per click per day (RPVD). Unfortunately, this metric ...
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0answers
31 views

When comparing variability between unequal samples, is there a way to correct for sample size?

I am trying to compare test measurements taken at three time points in a training paradigm. The data for each test consists of a number of durations in ms. The variable I'm interested in is the ...
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4answers
542 views

How to sample when you don't know the distribution

I'm fairly new to statistics (a handful of beginner-level Uni courses) and was wondering about sampling from unknown distributions. Specifically, if you have no idea about the underlying distribution, ...
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2answers
139 views

5 defectives rule of thumb

I have taught six sigma black belt classes using consultant sourced training materials which included the rule of thumb that when estimating the rate of occurrence of discrete events, like the ...
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0answers
33 views

non-parametric tests with significant difference in sample sizes

I have outcomes from a biological expt., where we have measured DNA lengths that has been affected. For condition1, I have 11 observations (length of DNA) and for condition2 I have approx. 116000. I ...
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1answer
121 views

Finding the sample space of an experiment

Suppose that a study is being done on all families with one, two, or three children. Let the outcomes of the study be the genders of the children in descending order of their age. List the sample ...
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31 views

appropriate sample size to fit non-normal distribution parameters

I have a population that, in theory, I could determine exactly. I am not doing so, however, because on my poor home computer, it would be too computationally intensive. Each calculation takes 45-90 ...
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27 views

small observations but many independent variables for multiple regression, can i have dummy variable?

The dataset i have consists of Y(N=80) and X(60 IVs). they are all numeric. I run multiple regression using two variable selecting methods: 1. stepwise 2. all possible regressions. I get very high ...
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21 views

randomForest sample size value formula

This question has been asked previously, but the answer didn't contain a formula - only a rule of thumb heuristic. Is there a formula or rule that exists for determining the appropriate sample size ...
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2answers
145 views

What's the minimum sample size required to do a time series analysis?

I'd like to know the minimum number of monthly data points required to do time series analysis with the seasonality effect in forecasting. I read some articles & they were saying that 50 or 60 ...
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0answers
37 views

How to calculate a required sample size for an estimate of the population total $\tau$ without knowing the population variance $\sigma^2$

To calculate a required sample size $n$ for estimating the population total $\tau$ (which is equal to $N\mu$) with a pre-specified error bound $B$, the formula is: $$n = \frac ...
2
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1answer
47 views

mean of population with repeated samples of varying size - how to apply CLT?

I have a population with mean $\mu$ and variance $\sigma^2$. I draw a sample with $n_i$ number of i.i.d random observations from population. I compute the mean for this sample as $mean_i$. I then ...
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35 views

Cross validation with unequal sample size for the left out sets

I am trying to do cross validation on several (20) subsets of samples, which all have unequal sample size. I cannot subsample so that sizes are equal. Example: batch 1: 500 samples batch 2: 400 ...
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1answer
48 views

Calculating sample size in R

I'm trying to calculate sample size and I have a Cohen F of .25, and I want to use power of .8. Is there a function in R that will let me calculate sample size based on these values? THANKS!!!!
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42 views

How to calculate sample size for poll / ranking

Let's suppose there are Y options to choose from. I'd like to run an experiment with a sample of n participants (from a larger population), each will choose 1 option from the Y alternative according ...