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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sample size of infinite population and alternative comparisson

I need to compare two alternative methods of manufacturing a product, say A and B. I wanted first to dermine the sample size of ...
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9 views

SPSS Comparing means between groups

I am currently working on a project about the performance of Himalayan mountaineering teams. I want to compare differences between these teams on the basis of the mountain they attempt to conquer and ...
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32 views

Appropriate Sample Size Formula

I have a uniform distribution set which contains different similarity scores. This similarity scores is linked with documents in which I am planning to examine. However, this set is big, and it is ...
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30 views

How to analyze survey data, interval or ordinal, and how to account for nonresponse bias?

I have a question regarding a survey. I gave a test to people and they were asked to rate the tester on a scale of 1 to 5, 5 being they liked it and gave it the highest rating, with 1 being the ...
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1answer
25 views

Clarification on the rule of 10 for logistic regression

Been brushing up on my logistic regression and I've seen a couple of things about the one in ten rule. To illustrate my current understanding (or lack thereof) lets consider a case with only two ...
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19 views

Is it correct to use a test dataset that is much bigger than the training dataset?

I am addressing a machine learning problem where I am simulating a reduction in the training dataset keeping a constant hold-outs sample for testing purposes. Usually a good ratio between training and ...
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35 views

Sample size when using GPS-trackers to analyze movement of reindeers

If one were to try and analyze the movement of ~2 500 reindeers before and after a (man-made) change in landscape have occured. Specifically how spread out the herd is, both as a whole and if there ...
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23 views

To work out 7 point Likert scale sample size, can I increase the MoE to 7%?

I have a survey that consists of 7 point Likert scale data. Each sample is quite expensive to collect, so I'm trying to keep the sample size as small as possible without compromising the results. My ...
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24 views

Friedman? Unequal samples sizes

my students were involved in three different simulations. I was asked them to rate their satisfaction with these simulations on a 5-point Likert scale (several items). Unfortunately, I have 60 ...
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1answer
17 views

Comparing retention rates with differing sample sizes

I'm looking to compare the retention rate of people who attended an event and those who did not. The list of those who did not (70) is significantly larger than those who have (28). Here is an ...
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3answers
522 views

Making up for a low sample size by increasing the number of observations

What exactly is the error that is made in the following judgement? "I cannot increase my sample size, so I'll make up for the low number of subjects by asking the subjects to perform more trials, ...
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22 views

How do “stacked” repeated samples influence our rules of thumb for minimum samples size in regression?

A professor in one of my graduate statistics courses once said, when briefly reviewing simple linear regression: "I would never EVER fit a line to fewer than 8-10 data points, it would make me ...
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2answers
33 views

How to empirically show that a certain quantity approximately follows a normal distribution?

To motivate some theoretical work, I need to show that two certain variables (say $X$ and $Y$) approximately follow a normal distribution in actual datasets. I have one large dataset with about $300$ ...
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28 views

Logistic Regression as Data Transform?

I'm analyzing medical research data with a small sample size that is not easy to replicate because the data were collected on an invasive procedure. The outcome variable is binary. There are two ...
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20 views

Experimental design for high dimensional model

I am running a computer model with a lot of inputs ( > thousands). I am not familiar with this area, so may I ask for any instructions/directions on how to make design on such high dimensional space? ...
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36 views

How to interpret LASSO graphs

I was given access to a total of 19 pieces of deceptive and persuasive texts along with a percentage on whether the readers of the said text followed through with the text's demands. The 19 cases ...
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11 views

Reference for Two-level Logistic Regression

I am an undergraduate student . In this level , we aren't taught Multilevel Logistic Regression. But my project topic is Multilevel Logistic Regression and I am ...
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1answer
16 views

Sample Size Calculation for intervention designed to decrease time to event outcome

I've been asked to provide a sample size estimate for a RCT of an intervention designed to reduce a waiting time. The investigator believes a reduction of 30 minutes would be important. As expected, ...
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1answer
53 views

About the central limit theorem and statistical testing

Wikipedia states that In probability theory, the central limit theorem (CLT) states that, given certain conditions, the arithmetic mean of a sufficiently large number of iterates of independent ...
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10 views

sample size query

I have a question regarding the sample size required for a project i'm involved in. Without going into too much unnecessary detail, we have processed 905 cases (in the last day) and 4 of them were ...
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1answer
27 views

Testing the difference between two samples with very different sizes using an un-paired t-test

I want to test wether population A is significantly different from population B (at 5% confidence interval). I need to do it for each variable using an un-paired t-test, since my data are normally ...
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1answer
20 views

Given a correlation matrix and sample size, how to calculate which correlation coefficients are statistically significant?

Suppose you are given a correlation matrix and a sample size. How do you calculate which correlation coefficients are statistically significant? If there are $K$ variables then there are $K^{2}$ ...
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1answer
93 views

Defining a Population

I am tracking monthly data entry errors in a customer service dept. of 20 people, and then doing regression and correlation analysis on variables like typing speed and data entry error. I have data ...
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8 views

Statistical significance in a small peer group

I am looking at the gross profit margins in a industry where there are 10 companies. The company I am interested in has a gross profit margin of 28% and the mean gross margin across all 10 companies ...
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1answer
25 views

Durbin-Watson Critical Values for Large Sample Sizes

My sample includes 3,627 observations but I can only find tables displaying critical values for the Durbin-Watson test for sample sizes 2,000 and below. Where can I find tables for sample sizes ...
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19 views

Minimum sample size for Factor Analysis? [duplicate]

What is minimum sample size required for using Factor Analysis? I have a data-set with 22 cases and 12 features. Is this sufficient? (I can't increase number of cases in my research, it is restricted ...
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1answer
31 views

Sample size calculation, linear regression

I have just had my viva and my sample size calculation was criticised as it was based on r2. I was told to base the sample size on the minimal magnitude of association. My outcome variable is HbA1c, a ...
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7 views

Sample Sizes Based on Cost Efficiency

I am planning a biology experiment that is testing the predictors of biological markers.These predictors are: Gender.(Binary) Smoking status.(Binary) Alcohol consumption.(Binary) Hiv infection ...
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35 views

Sample Size for Comparing two Measuring Tools

Let's say I have two devices that measure the same thing: the thickness of an object. Knowing that device 2 is more accurate and precise, I wish to see how accurate device 1 (how close do the readings ...
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2answers
123 views

Adjustable sample size in clinical trial

Most clinical trials I see have a fixed sample size. In some cases they have prior data that allows estimating the effect size and the variance or distribution of values, and calculate the sample ...
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12 views

Correlation computing time series data of unequal sample size

I am working on a computing a correlation between two variables X and Y. Both are time series and were recorded during the same period. 6/25/15. However X was recorded much more often than Y. ...
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36 views

Why sample sizes are often powers of two?

A layman's question: why are powers of two a commonly selected sample size? What are the practical reasons for setting them as such?
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34 views

Cluster Sampling involving Design Effect

A survey of residents is performed using cluster sampling. The design effect is 3.00. From the survey, the estimated proportion of people who are happy with their insurance company is 0.42 with a ...
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0answers
12 views

x and y standard deviation estimates in linear regression power analysis

I want to run a power analysis on linear regression against the null that the slope is equal to zero. Specifically I am trying to estimate what sample size I will need to obtain a specific power level ...
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1answer
141 views

how big to make k for cross validation

Is there a limit to how big you should make K for k-fold cross validation? I understand as K gets bigger performing the CV will take longer, but aside from that, is there any reason not to make K = n? ...
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What can we say about population mean from a sample size of 1?

I am wondering what we can say, if anything, about the population mean, $\mu$ when all I have is one measurement, $y_1$ (sample size of 1). Obviously, we'd love to have more measurements, but we ...
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21 views

Sample size for a small proportion

I'm calculating the required sample size for the following RCT design: the baseline proportion is 3%, and I want to be able to detect a difference of 1ppt with 80% power. If I use the sample size ...
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2answers
48 views

Relation between power and sample size in a Binomial Test?

$\beta$ (also called sensitivity or power) is a function of the sample size. It totally makes sense to me when we're performing a regression for example. The intuition is not that clear when we ...
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1answer
37 views

SEM - sample size and power

Muthén & Muthén offer a MPLUS based syntax for calculating sample size and power on SEM, using a Monte Carlo simulation. https://www.statmodel.com/download/FinalSEMsingle.pdf Is there any ...
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16 views

What are some major theories on picking the right number for the sample window size in time series analysis?

for example the number of samples to run the moving average, or the number of samples for sequential hypothesis testing. Or if there is a control scheme going on what is the best time window for an ...
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28 views

Use a model to reduce sample size?

I have a consultant that is proposing that he can reduce my sample size by using a model that is built off of previous samples. My first response was "NEVER EVER EVER EVER DO THIS". However, after ...
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1answer
23 views

sample size for metric survey data

I currently read this paper http://www.opalco.com/wp-content/uploads/2014/10/Reading-Sample-Size.pdf and try to understand sample size calculation. This paper presents Cochran's formular: ...
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27 views

Expected Euclidean distance between normal prior and posterior as sample size changes

Suppose the prior for some random variable $x$ is normal with mean $\mu$ and variance $v$. Denote the prior density by $f(x|\mu,v)$. Given normal likelihood with known variance $v$, the posterior for ...
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15 views

Longer panel has fewer obs?

I am using Stata 13 to analyze a panel. Recently, I received an update to the panel with a few more years. I ran the exact same probit regression including the longer time horizon. All used variables ...
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24 views

Incidence rate in a cohort with small sample size

I am dealing with the following problem: I have a small cohort of people with a specific disease (n=300) and studying the incidence of a related disease (which is kind of rare and normally occur only ...
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42 views

Sample size calculation for crossover design using dependent t-test - role of $\rho$?

I am trying to do a sample size calculation for a 2x2 crossover study. I have access to previous studies whereby I can get covariate adjusted estimates of the variability of the responses (from a ...
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1answer
24 views

Should the sample sizes be equal for non-parametric tests?

I randomized samples into two experiments and I ended up with about 190 samples in one group and 80 in the other. The distributions of the two samples are not normal and I want to use Wilcoxon test to ...
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19 views

Do I need to adjust the sample distribution to test significance?

The question in the title is probably not very clear, so let me explain better what my problem is. Suppose I have the following data from a survey: A categorical variable indicating the age of the ...
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1answer
68 views

Paired two one-sided t-tests (TOST) with unequal sample sizes

I have data from two populations (let's call them "before" and "after"), collected in a paired fashion. That is, I take a measurement under one set of conditions before, and then I can take multiple ...
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48 views

Correct Sample Size N in a Relative A/B Test with Binomial Variates

I randomly assign users to two distinct groups and track their return rate to the website (the return rate on each day for each group is simply $\frac{Number Of ReturningUsers}{TotalUsersOnDayZero}$). ...