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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How to choose the training, cross-validation, and test set sizes for small sample-size data?

Assume I have a small sample size, e.g. N=100, and two classes. How should I choose the training, cross-validation, and test set sizes for machine learning? I would intuitively pick Training set ...
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15 views

How to equalize lower accuracy on larger sample sets?

I have a collection of image samples that I want to OCR. I also have the ground truth of the text on these images. Now I OCR them and eg. 10 of 100 samples are wrong. So I got an accuracy of 90%. ...
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13 views

Formula for calculating sample size for hypergeometric distribution

Suppose you have an urn with "N" marbles. All marbles are either black or white. You take a sample of size "n" without replacing them to the urn. With this one sample you would like to be able to ...
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2answers
65 views

How to predict the amount of data needed for modeling?

Is there a way to estimate the amount of data (or the number of records) required to build a statistical model? I read few blogs and I feel that most of the responses concur that there is no way or ...
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19 views

Filtering Samples of Unequal Size and Correlating Categorical with Non-Categorical Data

Suppose I have a large number of samples, some of which only contain one observation, and some of which contain up to 12. Each observation can fall into one of four categories per sample. This ...
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17 views

How to find number of samples needed for a 95% confidence interval

I wish to perform a number of tests, what are the minimum number of tests I need to perform to be 95% sure the mean of the test is significant to within ±10% when I repeat the test ? As one example, ...
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171 views
+50

Bootstrap: the issue of overfitting

Suppose one performs the so-called non-parametric bootstrap by drawing $B$ samples of size $n$ each from the original $n$ observations with replacement. I believe this procedure is equivalent to ...
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2answers
33 views

Test for equality of coefficients from 2 different samples

I have a model that I fit on two different samples (each representing a region in a country, with different sample sizes): ...
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0answers
15 views

Determining Sample Size to Show Increase in Disease Prevalence

A prof and I are trying to figure out how many samples a study would need to show a certain % increase in disease prevalence, but I'm not sure I'm doing this correctly. Basically we want to know how ...
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19 views

Finding the fewest needed samples for a regression method

I have a regression method that I have applied with success to tens of thousands of well-observed objects. I'm looking to estimate how well it works on poorly observed objects. I selected 50 objects ...
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1answer
165 views

Is bootstrapping appropriate for this continuous data?

I'm a complete newbie :) I'm doing a study with a sample size of 10,000 from a population of about 745,000. Each sample represents a "percentage similarity". The great majority of the samples are ...
2
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1answer
45 views

Approximating sample distribution standard deviation

I've seen in video lessons that if the sample size is big enough (n>30) sample distribution standard deviation can be approximated by sample standard deviation. How do we get the sample distribution ...
2
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1answer
67 views

Power analysis from Bayesian point of view

I was reading an article on a power analysis and sample size calculations for a class of models that known as joint longitudianl-survival models. The paper derives a closed form formula for power and ...
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34 views

Sample Size Problem with Tukey HSD Test

I was planning to use a Tukey HSD test for the following data, as it was used in a study with a similar approach. I regressed stock data for three time ranges (1 year daily data, 2 years weekly data, ...
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1answer
56 views

Paired $t$ test - Different Sample size

In testing the difference between a 'pre' survey group and 'post' survey group, I have the same sample population surveyed, yet different sample sizes (fewer respondents within the 'post' group). Am I ...
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2answers
28 views

Cross Vaidation in Factor Analysis

I am trying to conduct an EFA with a sample size of 150 respondents. I would also like to use cross-validation but my professor says that the sample is not big enough for that. Is that true?
3
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1answer
36 views

Taking a random factor into account while measuring a proportion a low N

I need to be neat in measuring the success rate of a treatment. It is anyway pretty high. But as it is all about ecology, multpliying experiments is difficult. I have treated $N = 20$ individuals, ...
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2answers
39 views

How to obtain the standard deviation from means or confidence interval of the mean difference?

I am trying to calculate the sample size for a new study based on a previous one. The previous study compared means using a t test. I have: the means, the t test result, the confidence interval of ...
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0answers
12 views

Is this a valid way to find minimum sample size?

I have the following set of data from 5 specimens in a lab test. 1073 1016 1080 1100 1035 I 15 sets of these number for different types of specimens. I want to ...
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2answers
48 views

Should I perform multiple t-test or an ANOVA?

My causal comparative study seeks to three questions related to the hypothesis: a) is there a statistically significant difference between the academic achievement of 6th grade mathematics students ...
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1answer
54 views

Fisher's z-transform in Python?

I want to test a sample correlation $r$ for significance ($n=16$), using p-values, in Python. As I have understood from this question, I can achieve that by using Fisher's z-transform. Is there a ...
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20 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' ...
3
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1answer
71 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
33 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 ...
5
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1answer
75 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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0answers
23 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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2answers
97 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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0answers
20 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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0answers
15 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
38 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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36 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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1answer
12 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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0answers
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. ...
2
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1answer
82 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
58 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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46 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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0answers
31 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
71 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
22 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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19 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
87 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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0answers
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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0answers
92 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
65 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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40 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
55 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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0answers
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 ...
2
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1answer
109 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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0answers
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 ...
3
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1answer
176 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 ...