Questions tagged [sample-size]
This tag is ambiguous. Use it when the question is about sample size and NONE of the following are more appropriate: [small-sample], [large-data], [statistical-power], [underdetermined], or [unbalanced-classes].
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Sample size calculation in two different population for administration of a questionnaire
I need some help calculating a sample size.
I have two groups of people to whom I need to fill out a questionnaire. Group A consists of 45,000 people and group B consists of 3,000 people.
How do I ...
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Adequate sample size for non-normal population
There are 197,058 record holders (population) with an average of K shares each. I don’t know K, and the sample collected so far of ~24,000 observations appear to be non-normal (inverse gauss). I’m ...
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Calculating Sample Size from Prediction Equation (multifactorial linear regression)
I am conducting a study that seeks to assess differences in fat distribution in transgender women, as compared to cisgender men and women. A prior study has previously published separate formulas ...
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Sample population for AI Study
I have a study. I have 150 AI-generated images and 150 human-generated images. I have created a survey where respondents are given 10 images randomized from these 300 images. For each picture, they ...
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What does "roughly equal sample sizes" mean? [closed]
"Roughly equal" is ambiguous. My professor told me to use the cut off ratio of 1.5 to determine if my two sample sizes are roughly equal (i.e., n1 divided by n2) but I cannot find the ...
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How to do a power analysis for a virtual species distrubition model which uses random forests
I am creating virtual species distributions on a 100x100 grid (for now). Each layer of the grid represents one environmental variable. The "suitability function" defines the probability of a ...
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Compare CCDF of datasets with different sample size
I have 3 dataframes with the same structure (each dataframe includes a different type of tweet). Here are the columns of dataframes: id, ...
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Sample size - Diagnostic Accuracy Study
We have a gold standard test and a new test, and want to compare them prospectively, in a diagnostic accuracy study. I want to work out the sample size required. I have done some reading, and there is ...
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Calculating sample size when you have 2 treatments and uneven distribution
I have 2 new conversion webpages to test. Leadership recommends 80% traffic to existing conversion webpage and 10% each to the 2 new conversion webpages (non-negotiable)
How do I calculate sample size?...
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Minimum number of observation in multivariate regression
Given a multivariate regression, in a form bellow, what would be the minimum number of observations ($n$)?
$$\mathbf{Y}=\mathbf{X}\mathbf{B}+\mathbf{E},$$
where $\mathbf{Y}, \mathbf{X}$ and $\mathbf{E}...
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The difference in means t-test with unequal sample sizes
Someone I know are using linear regression to estimate differences-in-mean for parental stress, given a binary explanatory variable $X_i=[0,1]$. They have found a small, but significant effect.
They ...
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How to calculate effect size based on percentage and sample size?
In an intervention study, I have the following information - % of students passing an exam pre- and post intervention, sample size for control group and intervention group at pre- and post ...
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Sample size calculations for a pair-dependent discrete outcome
How do we calculate sample sizes (and power) for an outcome that is discrete and is only measurable between two individuals of a group?
Suppose we have $n_A$ individuals in group A, and $n_B$ ...
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Minimal sample size for difference-in-difference estimation of causal effect with time-series data
Suppose that Walmart has 1,000 stores. It has a 20% coupon for cereal, and it hypothesizes that the coupon will increase the sales of cereal by 3%.
Walmart wants to put the coupon in $n$ stores on ...
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assessing significance of difference between two groups using difference sample sizes
I am looking into assessing the effect of a condition. I have a population of several individuals that are not affected by this condition and a smaller proportion that is. Observations of a single ...
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What could lead to this misbehavior for the expected sample size (ESS)?
I am using Hamiltonian Monte Carlo (HMC) to sample the posterior of a continuous-time Markov Chain (CTMC).
However, after running 10 parallel chains with 100 draws each, the effective sample size (ESS)...
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Unequal sample sizes in two-way repeated measures ANOVA?
For a university course I'm doing research on the effect of veratridine in earth worm axons. We have tested 6 axons (less than expected due to time limitations) in three conditions: control (no drug ...
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Determine sample size to evaluate the effect of my solution?
I am currently building a solution that can reduce the overall electric consumption of a household by remotely controlling some appliances (for a period of 60 minutes).
And to prove that it works I ...
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What should be the sample size in a stratified random sample to get the same precision of a simple random sample?
I was reading example 3.2 on stratified sampling in Sampling: Design and Analysis by Lohr where a stratified random sampling design is proposed and compared with a simple random sample one.
The point ...
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P value is not significant, but most rates in treatment group are systematic higher than that in control group
I am analyzing adverse events rate in two groups, treatment and control group. There are about 10 different adverse events. Most of the rates are not significantly different between these two groups, ...
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How to calculate the standard deviation for the "final weighted mean difference" as in a meta-analysis for the purpose of calculating sample size?
I am seeing a Forest Plot presentation of the data in a meta-analysis. But the standard deviation for the final "weighted mean difference" is missing. I am wondering if it is possible to ...
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Using estimates for chi-square test for sample size estimation for logrank test
Is it possible to use estimates for chi-square test to estimate sample size for logrank test? I remember that I have seen papers that do it that way.
The problem is that, when you have to estimate ...
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relation between R-squared and sample size
Here is the question:
Suppose $X, Y$ are independent $N(0,1)$ random variables. And take the regression of $Y$ against $X.$ What is the relationship between $R^2$ and sample size approximately?
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General method for determining the sample size given the standard error
What is the formula for calculating the minimum sample size needed to achieve a specified relative precision for a given sample statistic's standard error, at a specified level of significance?
Mostly ...
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Can I do the Mann-Whitney test with different sample sizes 18 and 32?
Can a Mann-Whitney test be done on different sample sizes, one sample about 18 and the other about 32? The problem is looking at the difference in views of tourists and locals about the environmental ...
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Two proportion sample size calculation
Question
A drug maker wants to design a study in which two medications are compared. The first group has seen a improvement in 40%. Researchers want to see if the newer drug will improve this by 10% ...
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Sample size calculation for positive predictive value of test in cross-sectional study
I am looking for the right approach to do a sample size calculation for the positive predictive value in a cross-sectional study. From external sources, I know the prevalence in the population of ...
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How does sample size selection happen which is generally used as $20\times (p+q)$?
Can anyone explain me about how sample size selection happens which is generally used as $20\times (p+q)$? Here $p$ is the number of parameters in the final model and $q $ is the number of parameters ...
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Tools for reporting sample size that contains the percentage of the population
If we have a recorded percentage (statistic) on a population, if we take random samples we might not encounter the percentage till e.g. even we exhaust the population.
E.g. a box with $500000$ balls ...
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Power for hierarchical loglinear model
Can anyone point me in the right direction for doing sample size/power calculations for hierarchical log-linear analysis of nominal (frequencies) data? Would I get in trouble with reviewers for just ...
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I am looking for the right significance test for a questionnaire
I have a questionnaire to check the implementation of several recommended health improving measurements. It will look approximately like this:
Did you do your 20 minute Yoga routine on a daily basis?
...
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Which sample should I use for which model in the two step Heckman Approach for sample selection bias?
If I use the two-step Heckman procedure to counteract the sample selection bias, I have to set up both a selection model in the first step and an estimation model in the second step.
In order to ...
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Reduced effective sample size in balanced population after inverse probability treatment weighting
I am new to inverse probability treatment weighting (IPTW) and I am trying to understand it. However, I am not a statistician and I am having some troubles with advanced statistics concepts.
As far as ...
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Correct cointegration p-value by sample size?
I have several time séries couples from which I compute cointegration p-value, then sort these couple by that p-value, starting from the lowest (for further VECM analysis on the top 100).
All couples ...
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Exploratory Analysis with Small Sample
I'm using data (secondary analysis) to conduct an exploratory analysis. I have a sample size of $n = 67$, and the exploratory analysis includes two independent variables and four dependent variables. ...
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What should be the significance test when population size is unknown(know that it's more than 1M) and sample size is greater than 30?
I have a dataset with around 1M data. But, in real-life it should be more. From the dataset after first step processing for specific task, I got 50K data. Then I processed it again for a specific ...
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Assessing the Validity of Conclusions Based on Limited Findings
Introduction: Archaeological research often involves drawing conclusions about past societies and cultures based on a limited number of artifacts or findings. In some cases, such as the study of ...
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Statistical power and sample size for Poisson regression: specifying the "mean exposure"?
I am trying to perform an apriori power analysis to estimate sample size for a Poisson regression model. The background is that a RCT is proposed to compare the rate of pill consumption between two ...
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What is the sample size calculation for a discrete outcome (count variable)?
What is the sample size calculation for a discrete outcome (count variable)?
For example, I want to design a trial with a placebo and a treatment. The outcome is the number of days of treatment : 14 ...
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Linear model with different sample size
I have a continuous dependent variable and one categorical independent variable (with three levels). For the three levels, I have 42, 33, and 45 observations respectively. So, in short, I have unequal ...
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Is a response rate of a population considered the sample?
Let's say my survey population size is 1000 and I send a survey to all 1000. And only 200 responded. Is the 200 considered my sample size? If yes, can I calculate a margin of error on the questions in ...
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Sample size calculation cf. Alonzo et al
I would like to use a sample size method proposed by Alonzo et al.*
More specifically, I would like to use their sample size method for matched screen-positive studies (section 6 in the paper). I have ...
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Comparing two binomials with with partially matched sample
Imagine a scenario where I want to understand a population's support for a political candidate. I sample n=500 people randomly with replacement and ask them if they want to vote for candidate A or B. ...
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Are there special sample size calculations involved for the analysis of residuals in a contingency table?
This is a purely theoretical question (for the moment at least), so not a lot of details to share. If I plan an analysis of residuals following a chi-squared test of independence, I was wondering if I ...
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Is there a statistical approach to determine the minimum sample size for comparison of sums over time?
I have the number of items sold of various products over time from a supermarket. Each product belongs to a category of products. Some categories have a large number of items sold and some categories ...
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Split Sample for EFA and CFA with Smaller Dataset
I have a dataset (n=290) that I need to run an EFA. I was hoping to also run a CFA but I'm unsure if I have enough data to do a split sample approach. Please advise.
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Sample size and power analysis: Chi-square
Can someone help with a sample size analysis question?
Study design:
I have a sample randomly assigned to answer 1 of 5 different questions that vary in difficulty (1 - Easy -> 5 - Hard). The ...
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A/B test - sample size calculation and unit of measurement
Does the unit of measurement change how we calculate sample size?
For example, if we were to run an A/B test on ads with our target metric being click-through-rate, and we are doing a sample size ...
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When monitoring a sample, how to gauge when a substratum significantly exceeds sample size estimates and should therefore have its rates adjusted?
I'm in charge of a year-long, stratified sample where the population is estimated based on previous years but which is also quite dynamic, changing in unpredicted ways every year (furthermore, past ...
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Sample Size Estimation for Two Sample T-Test with Fixed Sample Size and Time-Varying Covariates
Let's propose we have a set of n heterogeneous study participants that independently from one another accrue salaries over time. We now want to evaluate a treatment to the study participants that is ...
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