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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This minitab blog suggests that very large sample sizes can be bad, what's going on? [on hold]

I often have sample sizes of over 10k so this is a bit worrying to me. Here is the blog page with several examples where small sample sizes appear to trump large sample sizes. ...
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8 views

Sample size calculation for multilevel, longitudinal experiment

I'd be grateful for any advice about how to do a sample size calculation for the following design. We are interested in the impact of two variations of an intervention on hospital in-patients' ...
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1answer
48 views

Optimal Allocation

A campus population of size N=9000 is to be surveyed by a stratified sample for the prevalence of a certain disease based upon three strata of respective sizes $N_h$ = 1000, 3000, and 5000 for h = 1, ...
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1answer
27 views

Standard deviation when sample is significant part of population

I know that sample standard deviation and population standard deviation are different, and are used in different cases (first when N>>n, second when N=n). But what when N>n, although not by much? For ...
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15 views

Significant difference between proportions, found at sample size below that suggested by power analysis

I'm looking at data from experiments that have been run to look for a difference between proportions, 1-tailed. In many of these it has been found that there is a significant difference between the ...
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16 views

G*Power analysis -sample size calculation

My experiment is devised as follow: There are two different types of stimuli-- cellphones: android (android-1; android-2) and iOS (iOS-1 and iOS-2). A sample size of 60 subjects are divided into two ...
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69 views

Can I do a t-test Power Analysis for Unequal Size Groups which Produces 2 Different Minimum n's?

It's usually straightforward to do a Power Analysis to compute the minimum sample size, especially in R which is my preferred ...
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16 views

Power Analysis for Text Mining

I have a population of 6 million text files with which I want to perform sentiment analysis (and text analysis more generally). I will need to manually hand code a subset of these texts into positive ...
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13 views

Determine minimum number of observations to be checked manually

I'm trying to classify transactions (say credit card transactions) as good or bad without looking at it manually. (The only way to figure out whether a transaction is good or bad is by manually ...
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1answer
23 views

sample frame representing the true population

(i) Is it true to say that if the sample frame is not a random selection (such as a convenience sample), then the sample frame is not representative of the true population? (ii) We can always do a ...
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28 views

Sample Size for SEM

Is there any formula for Structural equation modeling studies? I know there is a site: http://danielsoper.com/statcalc3/calc.aspx?id=89# Is there any good reference?
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32 views

Sample size calculation for paired ordinal data

What formula to use for sample size calculation for paired ordinal data? Imagine we have an intervention and we want to measure the effect based on before and after measurements of an ordered outcome ...
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1answer
10 views

How many samples are needed for a paired trial with multiple tries?

I'm having problem understanding how big sample size is needed for a situation where there are pairs in the before/after groups but these have all multiple data points. Problem Pose a situation ...
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7 views

What are some guidelines for sample size when constructing a Bayesian Network?

Both general advice and advice specific to my case below is welcome. I'm trying to contruct a Bayesian network with 20-30 continuous variables. I have 15 locations sampled, with 14 time points each. ...
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1answer
38 views

Sample size calculation for ROC/AUC analysis

As a background, I am not familiar with stats except on a basic level. I have been tasked with doing some analysis that is out of my comfort zone. I am trying to figure out how to compute necessary ...
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2answers
42 views

Sample size vs response rate, which is more important?

While I was preparing an internet survey, I read from multiple sources which says it is more important to have a high response rate than large sample size. Q1. I don't quite understand the logic ...
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33 views

Binary logistic regression: low event rate

I want to investigate how people (lets say smokers and non-smokers) differ in various characteristics. So I want to perform a binary logistic regression with SPSS. However, my event rate is very low ...
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28 views

Weighted piecewise regression to model proportion?

I was trying to model the relationship between utilization of service (from 0 to 1) and travel distance. First I binned travel distance by each 20 km and then calculate utilization for each bin (count ...
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1answer
45 views

Likert item as independent variable for ANOVA?

I am trying to analyze data based on a sample size of around 50 and would appreciate advice on which statistical test would be most appropriate. Participants, on a single questionnaire, were asked to ...
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1answer
16 views

Cluster Analysis Sample Size for Diss Proposal

My psychology dissertation will be a cluster analysis with one grouping variable. How do I know how many participants I need? I imagine there should not be more than 5 clusters. 79 items make up 9 ...
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18 views

Reference for Sampling distribution with varying sample sizes

I am looking for a reference on the sampling distribution associated with a population where each sample used to produce the sampling distribution is not of a fixed size n. Instead each sample will ...
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1answer
83 views

Logistic sample and case numbers

I have some questions about binary logistic regression. For my research, I am planning to use 12 predictors, and my sample consists of 129 cases. However, I know of a 1 to 10 rule. Additionally, my ...
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39 views

Questions about G*Power

Since I found an insignificant result, I performed a power calculation in G*Power. But I am not entirely sure if I input the right number in some fields. My design is a 2(between Ss) x 2(between Ss) ...
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85 views

Minimum sample size for a dichotomous outcome

I have two questions. I am running an experiment where I am interested in determining the sample size required for a certain CI and error, where values range between $<1$ and $>-1$. However, I ...
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1answer
56 views

Question about EFFECT SIZE

I have a question. If I found the effects of a variable is insignificant (p>.05), but the effect size d is 0.2 (small effect). So I used GPower to calculate the power and I found it is 0.14, which ...
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23 views

Calculating sample size. Repeated measures within subject

I'm trying to calculate the sample size for a repeated measures within subject experiment. I'm going to test the subjects under 4 conditions and for each condition 6 measurements are taken at ...
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1answer
44 views

Using R's prop.test function to compare subsets of a population

I'm new to CV, so please excuse any faux pas. I've collected sample data from a population and would like to discern whether or not the experimental group outperforms the control group. Let's say I ...
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9 views

How many quarters of observations are suggested before and after an event to determine the events significance in a time series analysis?

I'm reviewing a multiple regression time series analysis, and I'm concerned about the (possibly insufficient) sample size. The goal of the analysis is to determine whether an event during the time ...
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1answer
59 views

Calculating sample size with unknown standard deviation

I'm having troubles with understanding a problem which is basically asking to calculate a sample size (in order to estimate what portion of population has income more than 40K) with ...
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19 views

Calculating power for a survey to compare different metrics

I am currently planning a survey. The data will be used to test which of three metrics best captures some "true" underlying characteristic of the respondents. Getting data on the "true" underlying ...
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1answer
147 views

How big is “sufficient” sample size?

I am currently doing some tests with some specific parameter settings to characterize a process. I roughly remember that a widely used rule of thumb for lab tests and whatnot is a sample size of 5 or ...
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1answer
40 views

statistics t test sample size

in the formula for t test, t = (mean1 - mean2)/sqrt[(var1 + var2)/N] is N the total number of subjects in both groups being compared or the number of subjects in each group or condition? df = N-2 ...
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25 views

Choosing correct statistic aproach for dropout analysis

I need some input from you. At the moment, I feel a gap opening between theoretical knowledge and practical implementation. Problem case: In my study, I did an identic training program, around 10 ...
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1answer
47 views

larger sample size or more accurate measurement?

This question is completely theoretical in the sense that I don't have any real data. Suppose I am designing a study, in which I will go measure N pairs of (X,Y), then the goal is to build a ...
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1answer
32 views

Is it possible to have too much data? When should I subsample? [duplicate]

Social science PhD student here looking for a little help. I set out to collect around 300 online surveys for a study, but ended up with over 4,000. At that sample size should I sub-sample my ...
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12 views

How many tests do I have to run for this case?

I have developed a method to estimate a certain value called "flow" from 10% of the total data received (the total data may change every time) but of course there is an error associated with my ...
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21 views

Random sampling the data again to keep equal size across groups

I have an experiment with a between-group variable. It has 3 groups in total. When conducting the experiment, although we did random assignment for participants, the size of the 3 groups end up ...
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28 views

Is the variance of the residuals of a linear regression useful for estimating experimental sample sizes?

I have a data set of $y$ values that is not particularly normally distributed. However, the $y$s do partially depend on several other parameters. A linear regression model $y=c+\mathbf{ \beta ...
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33 views

How to handle unequal sample size with multiple factors?

The following dataset shows observations (count data) of cedar trees growing in small, medium, or large forest gaps (i.e. openings). You can see that that there is an unequal sample size and ...
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1answer
38 views

How to compare two classifications' classes' size?

I want to know if, between two classifications, one provides more homogeneous classes size than the other. I devised to use the chi square test (classes' size are far more than the rule of thumb of 5 ...
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13 views

Moderator Sample Size Discrepancy in Meta Analysis

I'm coding a meta analysis and have come across a paper that seems to have significant variation in the number of participants who answered specific demographic questions. The total sample size is $N ...
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1answer
16 views

Comparing participant numbers in a systematic review

I am doing a systematic literature review on theories for measuring user satisfaction. I have to rate the quality of these theories, and one of the criteria should be the number of participants in the ...
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51 views

Sample size requirements when studying total population

I work for a fundraising organization and we want to implement an A/B test to determine if a particular donor recovery technique is working. The population under study is our lapsed donors. These are ...
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17 views

Sample size required for bivariate normal distribution

I am new here. Would like to ask a question on the sample size requirement for hypothesis testing following. If I am drawing samples with 2 non correlated variables (say x,y) from a bivariate normal ...
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12 views

Does unequal sample size matter for single response

I am doing a corpus analysis on the relationship between the direction of signs and their valence ratings (from another corpus). I coded each sign as either upward, downward or non-vertical, and has ...
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2answers
31 views

Different number of samples affecting naive Bayes

I am trying to build a model of 7 classes text documents. However, i do not have equal number of samples for each class. I can have close to about 10k documents for class A but only about 100 ...
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18 views

Comparing networks of groups of unequal size

I want to compare some network properties such as entropy, connectivity, etc., between 2 groups. I have time series fMRI data on patients (n = 80) and controls (n = 30) for certain regions of the ...
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1answer
34 views

Percentiles and sample sizes

I have a data set of observations concerning an attribute that was collected over specific points of time. However, there are huge variations (hundreds to tens of thousands) in the number of data ...
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0answers
53 views

Sample Size Calculation for Cluster Sampling

I'm being asked to calculate a necessary sample size for a cluster sampling protocol. I don't have much experience with cluster sampling, so thought I'd come here. The situation is as follows: 1) ...
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27 views

Sample size and power

I came across a paper mentioning sample size calculation for 10% shift, 20% shift and 50% shift. I understand the SSC concept but what exactly is 10% shift and 20% shift.? So lets say for example if ...