Questions tagged [sample-size]

This tag is very ambiguous. Use it when the question is about sample size and NONE of the following are more appropriate: [small-sample], [large-data], [power-analysis], [power], [underdetermined] or [unbalanced-classes].

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17 views

Sample Size Estimate of Proportion

College admission office manually processes 1,000 applications in a month. We want to take a sample from this 1,000 to see how many applications were processed correctly (data entry errors, typos, ...
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33 views

Sample size calculation resulting in too high of a sample

I am trying to perform a power analysis to determine what sample size to use for an experiment after performing a pilot study. However, the sample sizes are showing values that are way too high and ...
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12 views

Could I compare two different samples with the same standard deviation? [closed]

The teacher hopes his new teaching strategy could fits in students with different levels of ability. So he conducts an experiment to meet his expectation. If there are two choice, (1)sample size: 30, ...
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10 views

Random sampling into two samples

I had a question about random sampling to create two datasets. Say I have a dataset $D$, with $N$ rows and $M$ columns. Each column is a feature $X_{1},X_{2}...X_{N}$, and each feature has an ...
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2answers
36 views

Linear regression - minimum sample size

I would like to perform a simple linear regression on data that shows a clear linear relationship. How to determine the minimum sample size for a simple linear regression analysis? My sample size is ...
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24 views

minimum replicate number for comparative metagenome

I am in the process of designing an experiment that will look for differences in the gut bacteria of sick and healthy animals. The question that has been troubling us is how many animals should we ...
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22 views

Repeated measures anova p-value not improving with larger sample size

CONTEXT: I have an experiment of 2 groups of 20 individuals each (40 people total). The test group received an intervention to aid them in converting leads and the control group did not. GOAL: I'm ...
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13 views

Determine necessary sample needed to assess true positives

I am trying to determine what is the sample I need in order to determine if a new method is as effective as an old one. So for example, in three weeks samples were drawn of 234, 229, and 163. These ...
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2answers
27 views

Reducing sample size for meaningful p-values

I'm analyzing correlations (using phi and chi-square) among pairs of items within a large dataset (1.2 million records). My understanding is that it's more likely to obtain spurious associations that ...
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1answer
115 views

Google Trends - Coronavirus [closed]

I played around with Google Trends and Corona because I was interested when people started to search for it. https://trends.google.de/trends/explore?date=2019-11-20%202020-01-09&geo=CN&q=...
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17 views

What is a valid sample size for Conditional Probability Tables?

I have a Bayesian Network model, for which I designed a study with the purpose of having empirically informed conditional probability tables (CPT). Below, I post the image of my network. The type of ...
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1answer
22 views

Calculate precision with constant sample size

Could somebody please help me to understend the following table? Is this a precision estimate for a given sample size? My colleage said that for this study, there is no formal sample size calculation,...
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25 views

Sampling big dataset

I am currently running some models on a very large dataset (instacart basket analysis, ~134MM rows) and was wondering on how to pick the right sample size to iterate and evaluate different models ...
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1answer
35 views

Is it better to have more data even if it leads to uneqal sample sizes?

I am comparing two approaches A and B using a t-test. I can easily obtain samples using A since the data is generated using a simulator. However, getting a sample using B is time-consuming and costly. ...
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1answer
30 views

Mixed Model Ancova

For a research project, I want to compute a Mixed-Design ANCOVA, i.e., a repeated measures analysis with one within-subjects factor (3 points of measurement) + one between-subjects factor (2 groups) + ...
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1answer
17 views

In survival analysis, how to calculate power from hazard ratio and number of events given alpha?

If I know number of events and hazard ratio, with given alpha, how do I calculate the power?
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26 views

How many datapoints needed to reduce AUC confidence intervals?

I am using LOOCV to calculate AUC and using the bootstrap BCa approach to calculate the confidence intervals. Now, I've read that the confidence intervals drop by root(N), is N the number of ...
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10 views

Estimating sample size for treatment on a continuous data with many zeros

I would love to hear peoples guidance/method on approaching this problem. I've have a large continuous reference dataset (n_ref=~50k) with lots of zeros (~95%). I need to estimate the number of ...
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21 views

How to Calculate Sample Size Requirements for Quasi-Poisson / Negative Binomial AB Test in R

I'm doing an AB test of two conditions, where the success metric is looking for an increase in the number of users taking a particular action each day. The variance is hugely larger than the mean, ...
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8 views

Derivation for the sample size formula of log-rank test in Cook and DeMets book page 129

Can anyone give me some hint on the derivation of E(xj|nj1,nj2), EU and VarU as shown on page 129 in the book "Introduction to Statistical Methods for Clinical Trials"? This is supposed to be a ...
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25 views

Sample size estimate for a ratio of sums

I need to do a sample size calculation for an A/B test. The metric is the sum of sales of items in a specific category divided by the total sum of sales of all items $$Metric = \frac{\sum_{...
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12 views

Sample size for stores AB testing with profit as the measurable metric

I have a group of test and control stores and I want to run AB testing on these stores to check if the proposed change in the Test store increase the profit by more than 1% from the control store. I ...
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9 views

Multi-arm RCT Sample Size External and Internal valid

I am trying to figure out the sample size for a multi-arm Randomized Control Trial (non-clinical) that will have internal validity and representative of the population, say; population X Any ...
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23 views

Sample size calculation : which sd to use?

Let say I've two independant groups where I have these informations : nA <- 20 mA <- 10 # mean sdA <- 4 nB <- 30 mB <- 15 # mean sdB <- 6 I ...
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1answer
35 views

How many examples do I need to show that a change in a feature causes a change in prediction?

not being a statistician I have a bit of a trouble to wrap my head around the following concept. Say I have a dataset $D$ of $N$ data points and a binary classifier (that was fit to some other ...
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18 views

How to calculate sample size in a dataset with multiple tests

i need some help. I just cannot figure it out on my own. I got told to find out if we already have enough participants (birds) for this study, so do a power analysis to calculate sample size. ...
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1answer
21 views

Power calculation & study design for study with rare safety outcome

An RCT is planned to compare a new/repurposed drug to placebo on the basis of mechanistic findings. Limited safety data exist. The primary efficacy outcome requires the recruitment of ~200 ...
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17 views

Correctly Specifying C=0 Sampling Plan

I looking for a little help with how to go about specifying/requiring the use of a C=0 sampling plan on an engineering drawing. In the past, we have typically been able to refer to a standard, for ...
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15 views

sample size advice for matching nominal variables

I have two databases of patients and medications. Each database has the same patients. Both have millions of records. My job is to select a sample from each and confirm that the medications match. ...
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14 views

required sample size for establishing equivalence of a gradient boosting model on different population

I have a trained Gradient boosting Trees (regression) model with a given R2 metric (obtained via cross validation) Now I want to verify that the same model is valid for a very different population. Is ...
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15 views

Effective samples size for quantile estimates with weighted samples

I've been reading the paper Rethinking the Effective Sample Size. In it, the authors provide an estimator for effective sample size given weighted samples (eq. 5.1 in the paper) which specifically ...
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20 views

Does it ever make sense to calculate correlation for a single individual when they are the full population?

Suppose I have a survey that I give to John. By giving this survey, I am only interested in John's answers and how he responds to the survey - he is therefore the true "population" (not looking to use ...
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10 views

How to calculate sample size for Likert Scale survey on student assessment?

I'm working on creating a survey where there'll be about 10-15 questions with 7-point likert scale. The survey is to be taken by reviewers who reviews the students' proficiency in taking images using ...
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23 views

Sample size calculation with cluster randomization for within subjects design

I'm in the process of planning a two group between subjects experiment and I want to calculate the required sample size. As the population I want to examine is not very large, it is rather ...
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1answer
37 views

Cochran's sample size formula p variable meaning and intuition

I want to calculate a sample size for a large population of about 50 million. I came across Cochran's formula and the finite population correction. In short, Cochran's formula is the following: $$ n_\...
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2answers
49 views

How are $n$ and $Var(\varepsilon)$ affecting to Variance of Estimation of Slope Parameter $\beta_1$ in Simple Linear Regression

Once I have derived the variance of $\hat{\beta_1}$ as: $\text{Var}(\hat{\beta_1})= \frac{\sigma^2}{\sum(x_i-\overline{x})^2}$ I would like to know how are affecting to this formula: the size of ...
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1answer
71 views

Understanding the 10:1 events per variable rule

I read online that 1:10 rule is based on the frequency of lower occurring class. I have a dataset with 4712 records. There are 1558 records labeled yes, and 3554 records labeled no. In my case, the ...
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27 views

Sample size estimation with known mean (optimal value), unknown stdv

quick question on sample size estimation. Let's say i play a game of poker, where i have 2 options, play or don't play. In the long run, the optimal strategy is to play 15% of all times, dependent on ...
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30 views

Sample size for the evaluation of Deep Learning Models

I'm evaluating the performance and accuracy in detecting objects for my data set using three deep learning algorithms. In total there are 24,085 images. I measure the performance in terms of time ...
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1answer
72 views

Sample size selection, known incidence rate distribution vs empirical

I want to estimate the sample size needed to compare binary incidence rate between two populations (based on binary separation to low/high risk groups). The known (previous research) incidence rate ...
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1answer
25 views

How to calculate the sample size for a categorical independent variable with a dichotomous dependent variable

Suppose that in a large population group you have 5 different ethnic groups, and you wish to calculate the prevalence of a disease in each ethnicity(percentage of people in each ethnic group having ...
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1answer
22 views

Clustering big dataset (12 million rows data) with categorical and numerical columns

I have 6 months of sales data (about 12 million rows non labeled) that i need to cluster. I am going to use 4 numerical and 1 categorical (2 levels) variable. As you can imagine the amount of the data ...
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1answer
33 views

Calculate sample size (or experiment repetition no.) with unknown population

I am running an experiment and I would like what is a good method to calculate how many times I need to run an experiment, in other words, how many data points I will need to collect. The issue is ...
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18 views

Strange sample size calculation method for one proportion using confidence interval

I came across with the following case in a clinical study regarding sample size calculation for proportion using confidence interval: "The expected value of the primary endpoint was set as 3%, and ...
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1answer
26 views

(Minimum) Sample size in a clinical study, rule-of-thumb

I was asked this question and I am not sure about my answer that is why I am asking it here. An institute wants to conduct a clinical study. This study has most likely three treatment arms. The design ...
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0answers
30 views

Is a Two sample T-test appropriate for my data?

sample 1: 9, 13, 30, 23, 34, 43, 39, 113, 4, 5, 11, 17 sample 2: 16, 25, 22, 67, 88, 43, 59, 39, 69, 93, 41, 231 The data is unpaired I want to calculate a confidence interval for the difference in ...
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25 views

Effective sample size of a time series of overlapping observations

Question: How do I calculate the effective sample size of a time series under overlapping observations? By overlapping observations of $x_t$ where the overlap is of length $k$ I mean a case where $...
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16 views

Does the large number of sample is the reason for low p-value in GOF test of Copula? (Cramer_Von mises)

I would like to determine a suitable copula function on my data. The multivariate computed from the original data is similar to the Plackett. The GOF test on my data with size 8000, reject all ...
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31 views

Minimal Sample Size needed to have at least one element when there are 3 possible outcomes?

This is my first question here, I am really glad this community already answered so many from other users that have greatly helped me. So here is my problem, I have a pretty "large" sample (N>200) ...
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30 views

Comparison of dispersion measures of different samples with different subsamples

Context: I have data on movie ratings and I want to find what factors affect the rating the most. I have $k$ features $F_1, F_2,\ldots,F_k$ characterizing a movie - for example, director, lead actor, ...

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