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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27 views
Sample size to conclude zero failure in a sub group from bigger population with known p [on hold]
Data shows a 5% failure rate from a test of 10,000 units of a product. Analysis of a subset of all units that were manufactured by Team A shows n=500 and zero failures.
Question is what is the ...
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7 views
Sample size calculation for survival analysis in retrospective analysis?
I need some reference to the following question:
I need some rules of a thump for a retrospective multivariate survival analysis. We are looking at cases that got cancer of urinary bladder, prostate, ...
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0answers
15 views
Determining sample size for a binomial distribution for a given confidence interval when the probability is close to 0 or 1
I've found formulas for determining sample size for when the probability isn't close to 0 to 1. However for the case when it is close to 0 or 1 I'm unable to find any formulas.
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0answers
27 views
How many items must be sampled to ensure that the sampling distribution of a sample proportion will be approximately normal?
I'm having some trouble on this. It deals with a sample size big enough to approach a normal distribution. Basically, the question is:
If a population proportion is believed to be 0.6, how many ...
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0answers
14 views
Pearson's r, Point Biserial Correlation, and Sample Size effects
I am currently trying to test a model for cross-cultural adaption and need to do a simple correlation analysis between the predictor variables (language ability, adaptive motivation, degree of culture ...
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1answer
24 views
Sample size for estimating success probability of a Bernoulli process
Suppose an AI player in a game can either win or lose. I wish to estimate the win ratio of this player. My question is, how many samples (games) needed in order to get an error smaller than 1%?
A ...
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0answers
6 views
distribution test among different sample sizes
I want to test 2 data sets with different scales. Data set A is 10K record, with about 200 outliers, and data set B has around 1K record with 20 outliers. How can I test whether the two data sets have ...
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0answers
14 views
Cohort Study Sample Size and Multiple Comparisons
I'm designing an epidemiological retrospective cohort study with a large number of exposures and outcomes, and I'm trying to figure out how many subjects I'll need in order to run all my analyses. The ...
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30 views
Sample size calculations for comparing area under curve (AUC) in ROC analysis in R
I have a dataset with a response variable and a predictor variable. I want to calculate the possible difference of AUC (delta) I can find with power = 0.8 and significance level = 0.05. Let's say I ...
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0answers
9 views
How to determine sample size for factorial experiment (2^3)
I am designing a factorial experiment with two independent variables at three levels (2^3). How do I determine how many samples to collect and how to allocate them. Further, after reviewing the ...
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0answers
42 views
Convince me that AIC can't be used to compare models with different sample sizes
Conventional statistical wisdom says we cannot compare AIC (or other information criteria predictive sample statistics) when the sample sizes for the compared models are different (See here for ...
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1answer
43 views
Why is the false acceptance probability not improving with increasing sample size?
We have a normal distribution with zero mean. We have two hypotheses for the variance $\sigma^2$:
$$H_0: \sigma^2=\sigma_0^2$$
$$H_1: \sigma^2=\sigma_1^2$$
We make $n$ independent observations $X_1, ...
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0answers
13 views
How to Calculate Sample Size for a two samples Welch's t test given a wanted power for an expeted effect size (without R)?
I have found no answer on web search engines for that. And even though I was able to find here some answers on how to calculate the power of a Welch's t-test here, they were expressed in R code.
As I ...
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0answers
28 views
Sample size and standard errors in OLS estimation
The standard errors of the estimated parameters from OLS estimation strongly depend on the sample size (n). Indeed, the standard errors tend to decrease when the sample size gets larger (ceteris ...
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0answers
29 views
Estimate unknown sum of iid random variables
Let $X_1, X_2, \dots$ be a sequence of independent and identically distributed discrete random variables with common mass function $f_X(x)$ defined for when $x \in \{0,1,\dots,N\}$ and $N$ is known.
...
0
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1answer
38 views
“effect size is independent of sample size” really?
I keep reading "effect size is independent of sample size" on the interwebs. Don't get me wrong, I get the practical vs statistical significance considerations.
What I don't get is that;
-power,...
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1answer
47 views
How big should be a sample size?
Question:
Assuming the population standard deviation σ = 3, how large should a sample be to estimate the population mean µ with a margin of error not exceeding 0.5?
My answer:
SE<= 0.5=3/√n ---> ...
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0answers
12 views
Sample Size Adjusted Metric for Calibration Curve
I'm creating a model that provides a predicted probability of an event happening. I am using calibration curves that plot predicted probability (x-axis) versus the actual event frequency (y-axis). I ...
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0answers
9 views
how to compute a minimal sample with some prior information?
Suppose N = 30, 000 students in total and a SRSWOR of size n will be taken from the population. And we want the proportion estimator ^p to achieve the precision with tolerance level e = 0.03, risk α = ...
0
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1answer
17 views
Comparison of means from different sample sizes
I have a data set which contains avg profit and the number of samples for each data point, no more information.
I'd like to compare the data points and decide which one to focus on more. However, I'm ...
0
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1answer
42 views
How can you compute sample size for a linear mixed model? G*Power only does repeated measures ANOVA
I read everywhere that repeated measures ANOVA is inferior to mixed modelling (since it doesn't handle missing data as well and relies on sphericity assumption). G*Power doesn't tell you how to ...
0
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1answer
25 views
Is there a systematic reason why a model trained on a subset of data does better out-of-sample than the same model trained on the full dataset?
I trained a linear regression model using 3000 data points. (OLS regression, no regularization.) Then I trained another model with the same predictors (about 25), but with a subset ($n=700$) of the ...
2
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1answer
33 views
What if you don't reach the optimal sample size?
I have used a binomial sample calculation to conclude that we need a sample size of 150, which for a response rate of 80% there is 80% power that the confidence limits between 71% and 89% cover our ...
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0answers
14 views
Analysis of multiple dependent variables all influenced by one indepdenent variable
I am analyzing a psychophysiological experiment.
I ran a model on my response times and accuracy data, which gave 7 parameters [dependent variable] per participant ( n = 12) all depending on one ...
0
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1answer
27 views
Optimal Sample Size/Power Analysis for Panel Data
I'm running a economic experiment. From a previous pilot I already know which size of treatment-effect I can expect. Each participant plays 20 rounds, so it't a repeated measures approach. I want to ...
0
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1answer
15 views
Sample size for 2 groups vs. one large group to measure spread?
I hope this question can simply be answered conceptually, without a specific dataset.
I am planning a new study, for which I will be testing the effects of depression on a memory task. I'm currently ...
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0answers
16 views
Effective sample size of a weighted sample
I am trying to understand the meaning of the effective sample size when we have weights for the sample. I have an intuitive understanding of why effective sample size can be less than the raw sample ...
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0answers
17 views
How to get the sample size to meet a certain power criterion
How should I find n (sample size) in the following equation?
$$p(Z<=-0.01\sqrt n-1.64)+p(Z>=-0.01\sqrt n+1.64)=0.95$$
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29 views
What is the minimum number of observations required for percentile calculation?
Here it is stated, but not justified, that percentile calculation requires at least three observations.
However, in this book the authors say that it depends on the percentile value (e.g., for the ...
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2answers
148 views
Power Analysis for a mixed two-way ANOVA with unqual sample sizes
I have a simple study design with a between-subject factor drug (real drug vs. placebo) and a within-subject factor time (three visits= repeated measures). I want to run a mixed two-way ANOVA and my ...
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0answers
9 views
Why under constant sample size I can get different guarantees on Type I and Type 2 errors, and MDE
I have been tricked by this basic question on hypothesis testing. Imagine you are setting up an experiment. The sample size is a function of the minimum detectable effect and the guarantees that you ...
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1answer
39 views
Build a statistical model based on small sample size
I hope my question is not too wide and that this is the right place to ask it.
I'm working in the field of spectroscopy and chemometrics. I'm building a statistical model to predict pollution levels ...
3
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1answer
39 views
Is there a general rule of thumb for how big the ratio ( Sample size / parameters in model ) should be?
I'm aware of model selection methods based on AIC and backwards/forwards selection, but I'm wondering if there is a general rule about how big your sample size $n$ should be (as an absolute minimum) ...
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0answers
6 views
Evaluate the relationship, if any, between the ordering of variables in a correlation matrix and the magnitude of the correlations
Given a correlation matrix, I would like to evaluate if nearby (in the row/column ordering) variables are differently correlated than non-proximate variables. That is, are the correlations a function ...
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0answers
13 views
Finding the minimum number of entries that will give me a confidence in the result
I have a big number of hotels, and each hotel has an number of price matches. There are two types of price matches : exact price match and price mismatch.
The number of price matches per hotel could ...
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0answers
31 views
Sample size confidence limit
I'm reading this text and wanted to know how they calculated the 95% confidence interval when calculating sample size and what it means:
"The sample size is 150 so that for a response rate of 80% ...
2
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1answer
34 views
How do you experimentally determine a minimum sample size to characterize a response?
I want to repeatedly perform a measurement until the distribution of response values stabilizes. Is there a standard metric to stistically conclude that new data does not contain new information? I ...
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0answers
26 views
How to do sample size calculation?
We are trying to use Binomial CDF to calculate sample size (assuming population size is infinite). However, we can only set confidence level, tolerable deviation rate and have no idea of how to get ...
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2answers
50 views
How to get any quantiles given median value and margin of error?
I am trying to get the values of the 25th and 75th quantile of the population based on two values that summarizes the samples:
median value
90 percent margin of error
I don't have any other ...
0
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1answer
42 views
Does confidence interval of the mean fully correct for size?
Say I have heartrate data at every minute during the day.
I suspect the person was exercising at different points during the day (based on some other data), and now I want to examine my hypothesis.
I ...
2
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2answers
41 views
What's the recommended approach when using hypothesis tests on a large sample dataset (1M+)?
What's the recommended approach when using hypothesis tests on a large sample dataset? Talking about 1M+ records.
According to this post (http://blog.minitab.com/blog/statistics-and-quality-data-...
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0answers
23 views
Long T Small N causal time series ols regression analysis ? can i use panel data? [closed]
I have N=28 AND T=260 WEEKLY DATA and i want to check impact of two variables on stock volatility.i proposed that one variable moderates others effect on stock volatility .
I was using time series ...
0
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0answers
23 views
How to calculate sample size for study design where observations are nested in study site?
I need to estimate the required sample size for a future study with a nested design and thus, mixed effect regression.
Sampling will take place at six plots per study site and observations will thus,...
0
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0answers
21 views
Determine sample size in power analysis
I have several confusions regarding estimating sample size. Consider the situation where I have data from a pilot, from which I estimated effect size and want to do power analysis (using software such ...
0
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0answers
9 views
Calculating sample size required for proving equivalence or superiority to population?
I am trying to determine sample size for a new approach to cancer detection such that the approach can be considered equivalent or superior to average population statistics.
In my case, I assume that ...
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0answers
13 views
Are my statistically significant results invalid if I fail to reach my desired sample size?
I conducted an unfunded study where 3 groups of 15 participants were observed over 11 timepoints. There were statistically significant between-group differences in slope and also statistically ...
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0answers
12 views
How to find the best representative sample for performing sentiment analysis on a large collection of texts
I'm trying to perform a sentiment analysis on a collection of reviews from Amazon. The dataset is about 500,000 rows and it's taking forever to preprocess the data.
I'm considering taking a random ...
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0answers
18 views
Comparing averages of unequal population sizes
Imagine the following problem: I have 1000 plots of land. On each plot of land I plant 1000 Oak trees and 1 Elm tree. Each plot of land differs in multiple parameters (e.g. sunlight, soil type, ...
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0answers
58 views
Logistic Regression Box Tidwell Large Sample
I am doing a logistic regression (binary DV) with 13 IV. As a first step I wanted to test the linearity assumption bw. the IVs and the logit. To do this I applied the Box Tidwell Method in SPSS by ...
0
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1answer
29 views
How large sample size for defining difficulty
I am currently making a website in which you can get several trivia questions. One thing I would like to implement is difficulty of questions. However, you can't just take a question and decide for ...
