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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6 views

Clustering and power: increasing the n but not the number of clusters

I am designing an experimental study with N observations from M sampled clusters, where M << N. Half of the clusters will be assigned to treatment. I can spend more money to increase the number ...
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1answer
10 views

Optimally sampling a sequence of observations

Given a multivariate population, I'd like to define a sequence of observations to sample, such that coverage and representativeness is optimal at each step (cumulatively). For example, a sample of ...
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13 views

power of regression coefficient tests

does anyone know how I can calculate the power of a regression coefficient test in R? for example we have: H0:B0<=9 and H1: B0>9 if actually ...
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2answers
61 views

Post hoc power analysis for a non significant result?

I have submitted a paper to a journal reporting a non-significant finding. One of the reviewers has asked me to include a power analysis on my data to work out how big a sample size I would need to ...
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2answers
10 views

Prospective power using observed difference

In my line of research we often calculate prospective power of a proposed study as a way to determine what sample size we should aim for. However, I'm often studying phenomena, or interactions between ...
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10 views

Power calculation for assessing relatively success two different predictors on a continuous outcome, Fisher r-to-z?

I'm thinking about a study where I assess the relatively predictive power of two different measures. Let's say a patient comes to a clinic on 3 different days, and 3 different measures of a noisy ...
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1answer
36 views

What is the empirical size of a test?

Now I am doing research of a proposed test statistic. I want to calculate the empirical sizes for different sample size of the proposed test statistic under the nominal type I error,such as 0.05. ...
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22 views

Calculate power of a test - solution verification

Let $X_1,X_2,\cdots,X_n$ simple random sample from gaussian distribution $\mathcal{N}(m,4)$. Calculate power of a test ($1-\beta$) for $H_0:m=0$, $H_1:m=2$, when significance level of a test is ...
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1answer
40 views

What does this mean “the standard deviation of a proportion is a function of the proportion itself”?

I was studying calculating power and sample sizes and i came across this paragraph: Calculating Power for comparing two proportions has the same idea as with comparing means, except that no ...
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32 views

Sample size needed to detect a three-way interaction?

I am hoping to propose a study for which the predicted outcome would be a three-way interaction. I am wondering if this is going to be possible at all with the resources at my disposal, or if the ...
2
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0answers
79 views

chi-squared goodness-of-fit: effect size and power

How can effect size and power of the chi-square goodness-of-fit test be calculated such that: Effect size is linear and standardized (given effect size $E_{x^2}$, $0 \le E_{x^2} \le 1$) so that ...
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1answer
23 views

Why is the noncentral chi-squared approximate of the deviance bad?

The statistical model under consideration is given by the independent realizations of two independent binomial distributions: $$ x_1 \sim \mathrm{Bin}(n_1, p_1), \quad x_2 \sim \mathrm{Bin}(n_2,p_2), ...
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1answer
37 views

Why is mixed factorial ANOVA more powerful than between-groups ANOVA

Why is a two-way mixed factorial ANOVA involving six conditions more powerful than a between-groups ANOVA with involving three conditions? I understand that between-groups analyses are less powerful ...
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0answers
32 views

Calculating the required sample size for a 2x2 repeated measures ANOVA?

I have conducted an experiment with two independent variables, each with two levels. I had one group of participants who were tested under four conditions. I have performed the ANOVA using SPSS, and ...
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1answer
12 views

Can interactions save power in a regression (vs. stratification)?

I have data with about 700 observations total. There are 9 subgroups in my sample with sizes ranging from 54-96. I want to use linear regression to explore how 8 independent variables might predict ...
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31 views

R code for multiple treatments power analysis

I tried the following code mentioned on this site- http://egap.org/content/power-analysis-simulations-r for multiple treatment power analysis in R. However, R mentions "could not find function ...
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0answers
29 views

Finding the uniformly most powerful test

Let $X_1,X_2,...,X_n$ denote a random sample from density, $f(x;\theta)={1\over 2\theta}$, $0<x<2\theta.$ Find the uniformly most powerful test for testing $H_0:\theta<=\theta_0$ vs ...
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21 views

finding the critical region of most powerful test

Let $X_1,X_2,...,X_n$ be from a density function $f(x;\theta)=3\theta x^2e^{-\theta x^3} ;x>0,\theta>0$. From the Neyman-Pearson Lemma the most powerful test to test $H_0:\theta=\theta_0$ vs ...
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1answer
50 views

Uniformly most powerful test in poisson

This is example in Hogg and Craig's book page 254 I have shown that the best critical region is $\sum X_i>=3$. I don't understand why, after finding $\sum X_i>=3$ is the best ...
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22 views

Power of t test with pwr package

I am not sure I understand what power.t.test(n,d) calculates, e.g. ...
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0answers
8 views

Is my loss of power in a combination study expalinable by estimating two GEE's?

I currently try program a combination test for longitudinal data and I am currently using GEE in R for that. I have a reliable sample size formula that gives me the desired power of 0.8 when I do that ...
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1answer
23 views

Is a single longitudinal model better than two independent analyses?

I'm planning to study a variable from a group of patients before and after a particular operation. I do not want to, or plan to, compare measurements across the "before" and "after" data (that is, I ...
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0answers
22 views

Why don't within-subjects ANOVA results change with more trials?

How is the increased precision from increasing numbers of trials reflected in within- or mixed-subject ANOVAs / why does it seem like it isn't? Assume I have a sample of 5 participants who did some ...
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16 views

Power calculation to test different intercepts in simple linear regression

I have two groups of data: patients and healthy controls. I perform a measurement and a modelled estimation of this measurement on both groups. I then calculate using simple linear regression ($y = ...
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0answers
10 views

Performing a power analysis for a cross validation study using C-test

I would like to perform a power analysis for a cross-validation study (training test 1:2) using C-statistics. When it comes to power analysis for to or z test I use G power software but I am not sure ...
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21 views

How does power change with small changes in mean (and effect size)?

So for the following groups, Group A has the (n=50, mean=50, sd=10) Group C has the (n=50, mean=53, sd=10) Group D has the (n=50, mean=54, sd=10) Group E has the (n=50, mean=55, sd=10) I have ...
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16 views

Calculating power of a test: Inequality inside normal CDF

As a part of an econometric exercise I need to calculate the power of a test for a least squares regression. The true value for the parameter is assumed to be $q=.9$ and the estimated parameter value ...
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13 views

Fisher Test power

I have a 2 by 2 contingency table, and I want to do a two-tailed fisher test. I have sample sizes n1 and n2 constrained, but how does one decide the two probabilities you can test for? For example, I ...
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30 views

Power Analysis for simple linear regression

I need to do a power analysis for a simple linear regression. I have one predictor and one response variable, I would like to determine an effect size (r2 in the lm?) from one species, and then use ...
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4answers
423 views

Do underpowered studies have increased likelihood of false positives?

This question has been has asked before here and here but I don't think the answers address the question directly. Do underpowered studies have increased likelihood of false positives? Some news ...
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2answers
219 views

Does a lower pvalue mean that test has higher power?

generic version of question: If you're comparing two statistical tests with different assumptions on the same data, and one gives a lower pvalue than another, does that mean that it has higher power? ...
4
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0answers
36 views

Categorical Variables With Little Variation. Chi-Square Test Power

Suppose you are trying to determine whether there is an association between gender and a rare disease, I suppose using the Chi-Square test. My intuition tells me that you must observe so many men, ...
2
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0answers
51 views

Can I calculate effect size using F, p and N (sample size)?

I need to calculate the likely/possible effect size of my study for a research proposal, based on the effect sizes of previous studies. The end goal is to determine the sample size needed for ...
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46 views

Sample size as proportion of population and statistical power?

I have done a study of information request response times in order to find out whether response time differs because of characteristics of the person doing the request. The studied unit is an ...
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0answers
33 views

SAS/STAT: Testing the significance for Email Marketing Control groups with Proc Power

I'm trying to figure out a way to test to see if my control groups for email margeling campaigns will produce statistically significant re sluts. The group counts have already been set. The control ...
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0answers
143 views

G*Power: ANOVA, repeated measures within-between interaction. Sample size seems low?

I'm trying to compute a priori power for a mixed ANOVA with one between factor (two levels) and one within factor (five levels). I set power to 0.8, effect size to 0.25 and alpha to 0.05, left ...
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1answer
112 views

Test for compairing data on same days in a week in different years

So I'm doing some power system analysis on active and reactive power loads and I'd like to compare the data from 2015 and data from 2015 to see how much they differ. The nature of the load is such ...
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0answers
27 views

Power calculations for interactions in repeated measures ANOVA

I am attempting to replicate a study in which the critical finding was an interaction between two within-subjects factors. How do I perform a power calculation that tells me about the sample size ...
2
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0answers
32 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 ...
3
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1answer
137 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 ...
9
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1answer
198 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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185 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
52 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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0answers
45 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 ...
1
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1answer
41 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 ...
2
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0answers
90 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 ...
0
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0answers
18 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 ...
2
votes
2answers
197 views

Multiple logistic regression power analysis

I have a logistic regression model and output an $R^2$ value. I then go and add another predictor variable to fit a second model. I can output a new $R^2$ value associated with the second model. When ...
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0answers
88 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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0answers
30 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 ...