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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15 views

Rule of thumb for sample size for mixed-effects logistic regression analysis?

Is there a simple way of calculating the minimum number of participants (and/or items) needed for a mixed-effects logistic regression analysis? In particular, what should I do if I don't know what to ...
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13 views
+50

Information criterion for selecting sample size when modeling tails

I want to model the left tail of an unknown distribution with GEV. Somehow I have to select how much of the tail to model. I am wondering if it is possible to create an IC for selecting between ...
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0answers
4 views

IT Conversion Sample Size [closed]

I have written a computer program that converts legal files from one format to another, say .doc to .pdf. I need to set up manual checks to validate that no data was lost/changed in the conversion. If ...
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0answers
14 views

Comparing differences in pairs of ratings using a bootstrapping like approach

I'm pretty new to bootstrapping like approaches. So I do apologize for any inconvenience. I have two independent samples, snow (n=120) and nonsnow (n=608), consisting of pairs of ratings on a ...
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1answer
37 views

Mulitivariable regression?

For my research project on the effect of a specific kind of surgery on clinical outcome, I want to study the correlation between the improvement in clinical outcome scores (ie the difference between ...
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0answers
16 views

Incidence rate sample size

Hi am trying to reproduce the following computation from a paper, but cannot acheive it. Sample size calculation was based on the combined incidence rate of moderate and severe hypoglycemic events ...
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0answers
52 views

Relative size of p value at different sample sizes BUT same odds ratio

Will the relative size of the p-value increase or decrease with the increase of sample size? My guess is that it will decrease, however, would it be the same case if they both have the same odds ratio ...
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1answer
23 views

How are sample size and confidence related when calculating Sample mean?

Maybe I'm getting ahead of myself and I should just keep reading my textbook, but I'm getting confused about something. Let's say a friend gives me 10,000 integers that he claims are normally ...
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0answers
27 views

What is the sample size when we take repeated measures?

Say we're running an experiment and we have 10 volunteers. From each of these 10 volunteers we take 3 measurements. So we end up with a dataset that has thirty rows. Say we're writing up the results. ...
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10 views

Beta regression sample size / power calculation

I'm looking for sample size calculation for beta regression with logit link. Could somebody give a link to a paper about it, or explain how it is done?
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0answers
14 views

Normalize(Scale) data before sampling or after sampling in binary classification?

I have a binary classification database with imbalance outputs (1 labeled data: 1400 samples, 0 labeled data: 200 samples). I balance data based on a criteria to (200 - 200). Where should I normalize ...
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0answers
28 views

Sample lower bound for binary classification in Linear Discriminant Analysis?

Below is a description of this problem: Suppose the label $Y\in\{1,0\}$ in binary classification satisfies $\Pr[Y=1]=\Pr[Y=0]=\frac{1}{2}$, and $p(X|Y=1)=\mathcal{N}(\mu_1,\Sigma)$, ...
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0answers
32 views

p-value and sample size [closed]

What would be the the p-value for a $\chi^2$ test when $n = 90$ when the p-value is .052 for $n = 60$?
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1answer
23 views

Unequal sample size one way ANOVA

I want to compare the means of X between BMI groups, but have unequal sample sizes between my groups. ...
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1answer
37 views

Apparent paradox about using a pilot study to determine sample size

I'm using some pilot data to determine the necessary sample size for an upcoming study. The primary goal of this study is to measure the correlation between two variables, A and B, and to determine ...
3
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1answer
69 views

Sample size when fitting categorical survey data

I have a model which fits data from repeated surveys: at time $t$, a number $n_t$ respondents is asked a question and can give one of $K$ answers ($k=1, ..., K$). This is repeated $T$ times ($t = 1, ...
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0answers
27 views

Sample size needed to validate classification/prediction model

Dose any rule of thumb exist (or possible calculation) regarding sample size needed to validate an binary classification model. We have developed this prediction model for a medical condition and ...
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4answers
35 views

Sample size of sampling distribution of the sample mean

When people say that the mean of the sampling distribution of the sample mean is equal to the population mean, is this true regardless of how small or large the size of the samples are? I'm having a ...
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0answers
18 views

Time-partitions of sample size

I am struggling with explain something I read in a Whitepaper. The essence is as follows. Let's begin with a random variable $X$ defined as number of events in an hours. Further, we assume that $X ...
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1answer
17 views

How does one determine the sample size and statistical analysis to be used?

How does one determine the sample size and statistical analysis to be used for an experiment wherein there will be two interventions (no standard medicine for positive control) A and B, and the ...
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1answer
14 views

Futility analysis sample size

I have been asked to determine the sample size needed to demonstrate futility in a small study. I suggested going the "traditional route" and conducting an interim analysis at a pre-specified ...
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0answers
38 views

Calculation of sample size

I'm doing a comparative study between two warming devices for patients undergoing renal transplant surgery.. patients are divided into two groups and are warmed by the device of that particular ...
0
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1answer
50 views

Sample size for categorical data

I have a population of phone calls - 200,000. There are different reasons for each call, but lets assume the number of reasons is known. i.e. 7 different call reasons: 1) Check on order 2) Cancel ...
2
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1answer
50 views

Confusion about the sample distribution.. Can you please enlighten me?

I thought that the sample distribution was an approximation of the distribution of the underlying phenomenon. But then the book says: We will denote the sample size by $n$ ($n \le N$) and the ...
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0answers
20 views

Sample Size Computation

I have defended against a group of expert panelist today and they all agreed that Slovin's is not longer accepted as a sample size determinant. I am really not a math genius and somehow goes slightly ...
3
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1answer
82 views

Effect of sample size in F-test?

Having worked hard to understand the t-test, I'm rapidly falling out of love with it. All that is required in the t-test to gain significance is increase sample size, which renders it close to ...
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0answers
22 views

weight of sample sizes in quasi-binomial GLM for proportion data

I'm studying a colonial organism, and my hope is to compare differences in percent survival between three treatment groups. The results are clear, there is a 55% difference in survival between ...
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0answers
19 views

imbalance in sample size at multilevel longitudinal data

I have longitudinal data (BMI level) measured at 3 time points and subjects are students nested to schools. The sample size in school level differs considerably (n=85 % in school 1, n=10 % in school ...
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0answers
27 views

How many samples are enough

I have objects with large number of attributes (about 60.000). Attributes are actually deviations of object part from model. I would like to cluster this objects, to get centroids that will represent ...
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1answer
111 views

Stepwise logistic regression

I am working with a dataset of 1000 individuals, 200 of which are disease positive. I have run a logistic regression with 25 predictors to identify overall which variables are significantly ...
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1answer
37 views

Why should changing the units of the variable change the required sample size?

I am trying to calculate the survey sample size necessary to estimate average rice yield. If the standard deviation is 10 tons, then the variance is 100. Plugging this into the sample size formula ...
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3answers
98 views

Why take multiple samples from a population?

I'm fairly new to Econometrics, and I'm curious about, when trying to estimate the population parameter, why it is important to take multiple samples of the population, instead of just combining all ...
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0answers
14 views

Optimal sample size

In a observational study, I found 30 deaths in 1st group and 10 deaths in 2nd group. In first group, total 1000 person were observed; in 2nd group total 1500 observation were observed. In statistical ...
2
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0answers
82 views

Sample size and power calculations for a randomized controlled trial

I need help with the power calculations to determine the sample size of a randomized clinical trial. This is a relatively simple trial with two arms: an intervention arm and a control arm. Patients in ...
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0answers
21 views

How do you assess data validity when sample size varies over time

Imagine that you have a customer feedback system where after a process people can press one of 4 buttons: (very happy, happy, sad, very sad) and an aggregation system reports how many people per hour ...
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0answers
64 views

Calculating sample size

I am going to conduct a research and would like to estimate the sample size that I will need. Here is the information that I have, please let me know if you need some more information. Thanks in ...
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0answers
18 views

How do I calculate the sample size required for a crossover AB|BA study?

I would like to know whether it is feasible to conduct this study. We have a subset of people in facility A (n=1300 per year), of which a proportion of these present a condition (n=18). Similarly, we ...
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0answers
2 views

Hilog-linear analysis for Categorical data

I found myself in a statistical predicament, and received a few suggestions from friends that didn't convince me a lot. I'm looking for advice on this predicament. I'd really appreciate it in advance. ...
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0answers
48 views

Sample size for tracking data

I'm currently trying to figure out how to estimate a fitting sample size for a specific problem. The situation is as follows: We've got x people, of whom we are able to track y% - all the time, so we ...
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1answer
71 views

Calculating Sample Size for Non-Inferiority Test in Cox Proportional Hazards Regression With Stratification

I have a binary predictor, X, in a Cox proportional hazards regression model, and I want to show that it is NOT a significant predictor. In other words, I want to show that there is not a significant ...
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1answer
50 views

How to calculate a sample size for validating correct/incorrectness of records in a data table?

I have read through existing answers on CrossValidated (plus elsewhere online) and can't find what I'm looking for, but do please point me to existing sources if I've missed them. Let's say I have a ...
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0answers
24 views

which method should i use for determining sample size?

what is the difference between the sample size determination method of using the critical values of the normal distribution with that of using the t-distribution? as an example if replication level ...
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1answer
23 views

Sample size for group comparison

I am collecting data from 3 different population groups (islands) and within each, comparing children from class 1 from 10-14 schools between two groups - those who completed kindergarten, those who ...
0
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1answer
46 views

must be a representative sample to apply factor analysis?

To apply the exploratory or confirmatory factor analysis, is what we should select a representative sample? And is there any condition to select this sample? I would validate a translated ...
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0answers
32 views

Reducing the amount of data by extracting a representative sample of my population

I have 6 B&W images representing different wavelengths (i.e. Landsat bands) of the Alta Valtellina (Italy). I extracted from the images only the areas of bare soil. Now, I want to perform a PCA on ...
3
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1answer
90 views

How to make sample space of the following question

My teacher gave me a question to solve.In the book of Ronald E. Walpole (Probability and Statistics for Engineers and Scientists), chapter no#3 exercise 1,question #2 which is as below: 3.2) An ...
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0answers
6 views

Accuracy results on subsamples

Given a binary classification task, let us suppose that a classifier achieves an accuracy result of $x\%$ on a sample of size $N$. What would be a way to calculate the conditional probability that ...
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0answers
34 views

Finding a confidence interval for observations being outliers

Suppose I have a sample with sample size $N$ that is obtained experimentally, e.g. I have counted the number of birds at a certain location at a certain time. Now suppose that the sample (the number ...
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0answers
20 views

Calculating sample size for a composite endpoint

I am trying to figure out how to calculate sample size for a composite endpoint. Say I have two groups, group A and B, and I want to know how they do after taking two different medications (let's ...
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0answers
21 views

Probability of taking a random sample of 24 measurements and getting a mean of at least 103.6 of true population

A random sample of size n = 24 measurements is drawn from a normal population. The sample has a mean of 103.6 and a standard deviation of 12.5. If the true population is 100, find the probability of ...