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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36 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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1answer
43 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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33 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 $$ ...
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1answer
31 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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12 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 ...
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0answers
35 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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10 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 ...
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1answer
25 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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32 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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12 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 ...
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2answers
54 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 ...
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20 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 ...
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0answers
11 views

Validity of testing the difference btwn 2 proportions with very low counts

I want to compare the mortality in the treatment group and the placebo, to see if they are different. I'm going through data from 37 drug trials. The problem is, in some of them there are very few ...
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53 views

Sample size calculation - Pros and cons of using one-sided z-test over two-sample differences in means approach?

I'm calculating the sample size required for an experiment with continous outcome variable. I'm considering two ways to calculate the sample size. One is based on a differences in 2 means test. The ...
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1answer
31 views

sample size determination

I want to do a teaching program on one of adverse effect caused by chemotherapy drug, out of 100 patients 31patients were affected, ,kindly suggest sample size if I want to prove my teaching program ...
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1answer
51 views

Difficulty with power analysis

I need to estimate sample size for an experiment but I am not very knowledgeable about power analysis. In my experiment, I am asking if a user can notice the two possible states of a system. I ...
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40 views

Finding a test statistic when you don't know the distribution?

I am working on this problem from my class and it has stumped me for a while now. I will show a picture of the problem and then my work/thoughts: Now we are not given the individual distribution of ...
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34 views

Power of a test

I need help with the exercise below: To investigate the effect of a new vaccine, 150 out of 300 sick animals were given the vaccine and the remaining 150 were given nothing. After a while, 10 of ...
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5answers
1k views

Why does increasing the sample size lower the variance?

Big picture: I'm trying to understand how increasing the sample size increases the power of an experiment. My lecturer's slides explain this with a picture of 2 normal distributions, one for the ...
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1answer
32 views

Confusion about confusion matrix, or why 'power of test' + $\beta$ = 1?

Consider a confusion table summarizing the outcomes of $n$ tests of hypothesis $H_0$ for $n$ independent experiments: ...
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1answer
42 views

Is there any possible method to calculate effect size in SPSS mixed model?

I run MIXED command for mixed model analysis of repeated measured data. However, there is no option or menu for estimate power(like partial eta in GLM) in mixed analysis. Is there any method to ...
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0answers
9 views

Including an interaction term in GLM with full factorial experiment data

I collected data from an 2 X 2 X 2 full factorial experiment. Because a DV is a count variable and unequal mean and variance, I ran a Negative Bimonial Model. It was hard for me to come up a good ...
2
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1answer
45 views

Can I justify using a one-tailed test in for this interaction effect?

I have an experimental setup with 2 factors, site and disturbance treatment. I have reason to suspect that plots at site A will be more affected by treatment than plots at site B. My response ...
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26 views

Question for constructing hypothesis test

I am trying to construct a hypothesis test for the $p$ parameter of Bernoulli distribution. My null and alternative hypotheses are: $H_0=p=0.5$ and $H_1=p1=p>0.5$ After some work I obtained a ...
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26 views

power of chi squared test for two proportions with gsDesign package in r

I have problem with calculating power for two sided chi squared test for the following design: Study includes 200 patients (100 patients per group). The null hypothesis is that p1=p2=30% and ...
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0answers
135 views

Simulation of Monte Carlo test

Using R, I am trying to simulate how the power of a Monte Carlo two-sample test for central tendency changes with sample size. However, my simulation results does not show power increasing with sample ...
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1answer
82 views

How to calculate sample size for this study design?

I am trying to find out whether the number of participants I recruited (N=42) so far is sufficient for my study in which: there are two interfaces (say A and B). ALL students in the study will try the ...
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25 views

sample size power calculation

This is probably very simple but I am struggling...in a population there is a disease present clinically in around 35% of patients, we want to use two tests which when used in parallel have a ...
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26 views

number of participants/analysis

Hi I am really struggling here any help would be muchly appreciated, please use laymen terms where possible. research question: a comparison of quit rates between 3 smoking cessation treatments. ...
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0answers
74 views

Power calculation for a coefficient in linear regression

Consider a simple linear regression of the form: $$ Y \sim \beta_0 + \beta_1 X + \beta_2 Z + \epsilon$$ I have questions regarding calculation of power for $\beta_1$. To calculate power, I approached ...
2
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1answer
69 views

power to detect effect sizes for the usual t, Welch Adjusted t, and Mann-Whitney U test

For class, I am given a series of sample sizes and variances for two groups and am asked to calculate the power for detecting effect sizes for the usual t test, Welch adjusted T test, and the ...
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2answers
153 views

5 defectives rule of thumb

I have taught six sigma black belt classes using consultant sourced training materials which included the rule of thumb that when estimating the rate of occurrence of discrete events, like the ...
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1answer
29 views

What is the statistical power of a test when the true population mean is unspecified?

I have been given the following homework problem: To improve the reading scores of its students, a school district randomly selects 50 students to participate in a new program. The mean reading ...
3
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2answers
111 views

Empirical rejection rate of a wrong null hypothesis -is it the “power of the test”?

I guess this is basic, but it forms part of the holes in my statistics education. What I know is that the power of a hypothesis test is not a fixed magnitude, but a function of various factors ...
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2answers
126 views

Calculate necessary “treatment group size” for power in a regression setting

I have an observational quasi-experimental study, where I try to estimate the effect of a "treatment" (participation in a programme) on a continuous outcome. Participants (some two-thirds of all ...
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2answers
186 views

Example of an inconsistent Maximum likelihood estimator

I'm reading a comment to a paper, and the author states that sometimes, even though the estimators (found by ML or maximum quasilikelihood) may not be consistent, the power of a likelihood ratio or ...
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1answer
61 views

How to choose a Power and Alpha combination for a fixed sample size?

Let's say I have a sample size established with alpha=0.05 and power=0.8 (based on time constraint for study). The same sample size can be achieved with any of: ...
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1answer
348 views

Why is usually the acceptable probability of type 1 and type 2 errors different?

This question is raised by my supervisor and I don't know how to explain. Usually the accepted confident level is 0.95 which means that the probability of type 1 error is 5%. But the usually ...
2
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0answers
37 views

Calculate statistical power on groups with different size

Is it technically possible to calculate the statistical power for a test where the two groups don't have by design the same size. I'm thinking to a 90%-10% split of the population. Namely, is there a ...
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1answer
21 views

Increasing statistical power by having a highly sensitive outcome measure

Is it logical to say that you can increase statistical power by having a highly sensitive outcome measure? I say this because a highly sensitive test has low Type II error, and low Type II error leads ...
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1answer
64 views

When testing for a difference between effect sizes, is test power affected by their respective magnitude?

When comparing two effect sizes with a statistical test, does it matter for the test's power whether these effect sizes themselves are large or small? Imagine you are planning an experiment in which ...
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1answer
103 views

Effect of sample decimal points on power in rank-based tests

I perform different rank-based non-parametric tests (Friedman and Nemenyi) post-hoc and noticed that the decimal places of the samples have a strong effect on their power. Please consider the ...
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2answers
886 views

Post-hoc tests for MANOVA: univariate ANOVAs or discriminant analysis?

I am using a MANOVA test to compare nine different dependent variables (from neuropsychological and neuropsychiatric assessment) between three groups. The output shows a significant influence from ...
0
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0answers
224 views

How to calculate post-hoc power analysis for multiple regression models?

I have few questions that came up while I was trying to calculate post hoc power analysis for a regression model: I calculated post hoc power analysis for a regression model that produced a ...
2
votes
1answer
168 views

Power analysis from Bayesian point of view

I was reading an article on a power analysis and sample size calculations for a class of models that known as joint longitudianl-survival models. The paper derives a closed form formula for power and ...
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2answers
166 views

What does a post hoc power analysis say about the significance of the study results?

I orginially posted this over at AskMetafilter, and a commenter suggested I ask it here. I work for a dietary supplement company that also makes skin care products, and some of those skin care ...
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0answers
31 views

T-Tests and Regressions

my supervisor has asked me a few questions that I'm not entirely sure how to answer. For a quick summary, my study includes a small sample of 16. To describe the sample, I compared the scores of the ...
2
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0answers
40 views

power of poisson test with large sample size

I would like to compute the power of two distributions which are poisson with $n_1$ being large and $n_2$ being medium sized. I have used the formula given by Krishnamoorthy and Thomson for the C-test ...
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0answers
18 views

Statistics:Power Question Update [duplicate]

I have already asked this question but I did not initially give out all the details on the question, like the question being a multiple choice question. You manufacture and sell a iron rod whose ...
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1answer
164 views

Significant difference between proportions, found at sample size below that suggested by power analysis

I'm looking at data from experiments that have been run to look for a difference between proportions, 1-tailed. In many of these it has been found that there is a significant difference between the ...