Is a property of a hypothesis testing method: the probability of rejecting the null hypothesis given that it is false, i.e. the probability of not making a type II error. The power of a test depends on sample size, effect size, and the significance ($\alpha$) level of the test.

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9 views

Power and sample size [on hold]

I would like to test the agreement between two similar imaging tests. How do I determine sample size to power the study? I'm looking for a 10% difference and p<0.05
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0answers
8 views

Power calculation for multiple level clustering / randomization using simulations R

I am trying to calculate power of the following design: -Treatment is randomized over a small number of clusters (1st level clustering=regions) -Within each region we randomly select villages ...
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32 views

Boschloo or Barnard? Which Test for Cross Table Analysis?

Actually I am analyzing a 2x2 table from a small dataset of 30 patients. We are retrospectively trying to find some variables that give a hint about which treatment to choose. The variables (obs ...
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1answer
43 views

What are the ''desirable'' statistical properties of the likelihood ratio test?

I am reading an article whose method is fully based on the likelihood ratio test. The author says that the LR test against one sided alternatives is UMP. He proceeds by claiming that "...even when ...
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0answers
30 views

How to calculate the sample size for proportions using Effect Size?

I need to determine the sample size for my experiment. In my experiment I will select a set of x projects, from a population of N project. For the sample x projects will apply a treatment to know the ...
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1answer
22 views

Unequal sample sizes in t test with homogeneity of variance

I have looked at the other similar questions on here, but I can't seem to understand whether power is still an issue for unequal sample sizes with the homogeneity of variance being met. Yuen (1974) ...
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34 views

Power Calculations in R for ANOVA's

I need to use R code to calculate the power of a Nested ANOVA. I want to detect a 3% difference between two consecutive tests between a stage in a process. The tests are identical and material has ...
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1answer
24 views

Can you infer that sample is representative from statistical power?

I have travel times for 1000 routes (origin-destination pairs) and I collected about 12 actual travel time samples by driving some of these routes (randomly selected out of the 1000). I calculated ...
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0answers
44 views

Power of a Interaction term in R

I have analysed a dataset with a linear regression model, including an interaction term between a binary variable and a continuous variable. The interaction was significant. Afterwards, I have fitted ...
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12 views

Calculate Sample Size for a Price Change for Specific Group

Say I operate a tour bus. For every tour I run, I offer guests the option to buy a camera. The camera currently costs 5. I know average purchase rate is 40 percent and the standard deviation per ...
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34 views

Multiple Logistic Regression power analysis

So I have a logistic regression model and output an R² value. I then go and add another predictor variable to a second model. I can output a new R² value associated with the second model. When I run ...
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19 views

How should a sensitivity power analysis be interpreted?

I recently ran an exploratory experiment which manipulated several factors in a full factorial design. There were some clear visual patterns in the results, and a basic ANOVA found several different ...
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21 views

Post hoc power analysis in genetic study

We have performed a genetic study and a post-hoc power analysis is requested. Subjects have been divided in group A (n=162) and group B (421) on the basis of their expressed phenotype. The subjects ...
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2answers
34 views

Can a linear relationship between estimated standard deviations and estimated means be used to increase the power of a t-test?

Let’s say I have a high number of treatments (40) but a low number of replications per treatment (n=4), and I am interested in comparing values between two particular treatments (let’s say treatments ...
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34 views

Why am I finding greater power with a coarser level of randomization?

I am working on a Monte Carlo power analysis for an experiment about the hiring of teachers in schools. We can randomize the treatment at the school level or at the applicant-school level. I was ...
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1answer
44 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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18 views

How can I determine the power of a bootstrap confidence interval?

I'm halfway through an exercise for my statistics class, but completely stuck, and unable to find an answer online or from more statistical friends. Simulating n = 6 observations Xi ∼ Poisson(6), we ...
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1answer
38 views

Should I bother that t-test power is relatively small when H0 is already rejected?

I have two quite small samples ($n=7$ for each) and I get two-sample t-test power for them 0.49, which is relatively small (calculated by R power.t.test()). ...
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1answer
75 views

How would combining levels in a contingency table (2x3 $\rightarrow$ 2x2) affect the power of a chi squared test?

A 2x2 table has a critical $\chi^2$ value of $3.84$, whilst a 2x3 table has a critical value of $5.99$ (for a significance level of $0.05$). Is it reasonable to think, that if you are able to turn ...
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31 views

Basic Power test and Power test using ncp do not match

I am referencing 18.5 section of http://www.cyclismo.org/tutorial/R/cholesterol.html ,data is available to download and test. The case study asks to perform a ...
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67 views

How do I calculate the effect-size of an unequal sample size independent t test?

Given the following parameters, how do I calculate the effect size of an independent unequal sample size t test? ...
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1answer
29 views

Sample size estimation for MANOVA

I am trying to run a replication of a study which used a factorial design (2x2) with three DVs (dependent variables) and subsequently ran three ANOVAs to test their hypotheses. Given that the DVs in ...
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0answers
25 views

Confirming failure to reject null hypothesis in Fisher's exact test

I have the following data and am trying to determine if the manual treatment is better at getting a correct response in each category (confidentiality, authenticity, and integrity): Using Fisher's ...
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86 views

How did they power this study? (One sample proportion test)

I was asked to perform a sample size calculation for a study with a single arm and a binary outcome. They have given me an assumed proportion, $p$, and need the upper 95% confidence interval to be ...
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2answers
56 views

How to compute Shapiro-Wilk test power?

I test normality of 12 residuals that are obtained from resid(lm(...)) command via shapiro.test. Thus I know variance, mean, ...
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2answers
57 views

If underpowered for three way interaction, but two way interaction is still ok?

I ran a three way 2x2x2 ANOVA (AxBxC) that turned out to be just shy off a significant three way interaction (p = 0.06). I ran the two way interactions for AxB for the 2 levels of C anyway. As it ...
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27 views

Losing power by doing repeated measure instead of standard anova

I have an experiment with one within subjects factor. It has 3 levels: sleep deprived (24 hours), sleep deprived (12 hours), not sleep deprived. Over the course of 6 weeks we run a counterbalanced ...
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1answer
59 views

Rejecting Null Too Frequently in Poisson GLMM (lme4, glmmPQL, glmmadmb)

While trying to determine power for a Poisson GLMM, I started by checking the probability of rejecting the null for a given parameter when the null is true (parameter is zero). I kept coming up with a ...
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1answer
38 views

Which of the following when performing a statistical test is NOT a Random Variable?

For a test for my stats class, we were asked, "When performing a statistical test on a sample, which of the following is NOT a random variable?" A) The Test Statistic B) the p-value C) The power of ...
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38 views

How should I calculate required n for minimum power of a sequence of parallel or simultaneous tests?

I am concerned with the practical situation in which I design a 'no-budget' split-ballot 2 x 1 experiment. We have money for $n=80$ cases in total, thus $n=40$ in each of two groups. In total I will ...
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0answers
58 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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0answers
27 views

Binomial data: Null Hypothesis $p = 0$ when all Sample Values are 0 - testing and power analysis

I am trying to investigate if the proportion of successes in my population can be shown to be larger than zero. Thus, $H_0: p = 0$ and $H_A: p>0$. Since $p=0$, the prop.test in R does not work, ...
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36 views

Power calculation for non-significant pilot study?

I have performed a pilot study comparing the means of two groups and I've yielded non-significant results. I wish to determine whether increasing the sample size would have produced a significant ...
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1answer
44 views

Show that power of size $\alpha$-test is larger than power of level $\alpha$-test

I have two power functions of the null hypothesis, $Q(\theta_0)$ and $Q^*(\theta_0)$ where $Q$ represents $\psi(\mathbf{y})$, a size $\alpha$-test, and $Q^*$ represents $\psi^*(\mathbf{y})$, a level ...
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100 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 ...
2
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1answer
41 views

Does an underpowered mediation/moderation SEM have an increased chance of Type I error?

A study I'm familiar with has been encouraged by its review board to take more participants. This seems a sensible request on general grounds, but the reviewers suggested that it was essential to ...
2
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1answer
22 views

Power of a composite test

I know that power function is defined as $\beta(\theta)=P(\mathbf{X}\in R\mid\theta)$, where $R$ is the rejection region. For a composite test, $\Theta_0^c$ is a set. How do we define "the power of a ...
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1answer
40 views

whats the minimum number of time periods needed to get a rewasonable statistical power

I'm running multiple regression analysis with 3-7 indep. variables using macroeconomic indicator data from the World Bank. MOST of the World Bank data sets begin no earlier than 1990, which means my ...
2
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1answer
611 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 ...
2
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1answer
321 views

Determining sample size for proportional hazard

I am in the design phase for a longitudinal study examining the effect of a predictor (neighborhood risk score) on time to an outcome (re-arrest), as well as whether or not the variation explained by ...
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0answers
171 views

Deriving the power formula of the one-sample proportion test

I have to derive the power of the z-test in testing $$ H_0: \pi=\pi_0 \text{ versus } H_1: \pi>\pi_0 $$ Denoting by $p$ the sample proportion, the power equals $$ ...
2
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1answer
69 views

R power.prop.test and power equation in the difference between proportions

I am looking into the formula built into the R function power.prop.test{stats} and I am stuck trying to understand the following calculation: ...
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0answers
25 views

Power analysis and high-dimensional penalized regression

I'm fitting a Lasso regression for a continuous response y and p covariates X (p>>n=# observations). I'm interested in assessing the power in detecting a given covariate that I know to be active. I ...
2
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0answers
42 views

computing power in R

How can I compute the power of Dixon discordancy test in R. As there are functions for many other tests like t.test, ANOVA, proportions test etc. but not for this one. Any help will be warmly ...
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25 views

Fully crossed repeated measure power

I would like to do some a priori power estimation to see what type of sample size I'd need for an experiment. It's a fully crossed 2x2x2 repeated measures design. There are 3 factors with two levels ...
1
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1answer
45 views

power for mixed-effects model

I wonder if there is a simple way of calculating an achieved power for a mixed-effects model. The fixed effects are the intercept and a slope. The random effect is for the intercept at the two levels ...
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0answers
62 views

Calculating Power of a sign test

I'm really stuck on part (e). I want to calculate the power of the sign test. So to find the power of first test. I let $M$ be the number of observations greater than $4.7$. Now I need to find Power ...
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29 views

DOE Power Calculation for Interaction Terms

I was using Monte Carlo to determine the a-priori power for the terms in a designed experiment. To do this I used the following procedure: Set an effect size I expect to see in my response Use the ...
4
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2answers
93 views

Why is the complement to Power not $\alpha$?

i) Wrongly rejecting $H_0$ is called a type I error (controlled by $\alpha$). ii) Wrongly accepting $H_0$ is called a type II error (the probability of which is indicated by $\beta$). iii) Power is ...
2
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0answers
36 views

Averaging time series to improve stationarity - loss of power?

Short version When averaging over a presumed stationary time series and calculating statistics (e. g. normalized mean square error) to compare to a simulation (atmospheric turbulence model) of the ...