An inquiry into the quality of a statistical test by calculating the power - the probability of rejecting the null hypothesis given that it is false - under certain circumstances. Power analysis is often used when planning a study to determine the sample size required to achieve a nominal level of ...

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19 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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2answers
23 views

Using Kruskal Wallis vs One Way Anova with small sample size

I have an experiment with one factor and five levels. The response is proportion of conversion (ex: 1/11, 1/8...). Doing a power analysis: ...
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1answer
43 views

A question on accuracy of hypothesis testing

If I am doing a hypothesis test with a sample of 100 from a population of 1,000 it would be more precise than doing a test with a sample of 100 from a population of 100,000. How can I show this? Is ...
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26 views

Power Analysis for Logistic Regression with one nominal variable

How do I estimate sample size or do power analysis for logistic regression with one nominal independent variable? Is there a way to do it with Stata?
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1answer
48 views

Sample size estimation for test for proportions

I'm interested in finding out if a particular activity increases the chance of a particular segment of prospects converting to a client. I would like to be able to detect a 5% difference in overall ...
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0answers
17 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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10 views

Power analysis for environmental microbiology samples

In my experiment, I will be taking environmental samples in cheesemaking rooms of 20 dairy farms (each sampling point is a 10cm x 10cm square area that I swab and count the microorganisms I found back ...
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0answers
38 views

Required sample size with unequal variances

I have a setup with equal sample sizes ($N_1=N_2$) from two groups (sample means $\mu_1$, $\mu_2$), but different variances $\sigma_1^2$, $\sigma_2^2$ in both groups. If the variances were equal, ...
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8 views

Power of a case control test as a function of P(X=1) & P(Y=1)

For our course in statistics we had to build a simulation which would give insight in the power of a case-control study vs that of a cohort study, both trying to discover an association between 2 ...
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20 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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10 views

relationship between power means and population zscore calculations

Can one use a power mean of the ages in a room to determine the age break down of a room? Let's say you have a room full of people, by using the average age and standard deviation of the age, how do ...
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1answer
47 views

Method to determine the sample size for a one-sample t-test

What method is appropriate to use for determining a sample size for one sample t-test? How can I conduct the power analysis in this case? I am looking for the analytical formula that would allow me ...
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1answer
25 views

Averaging effect sizes?

Suppose I need an estimate of effect size for a power analysis. I read the relevant literature and calculated Cohen's $d$ from some number (3) of studies. If the Cohen's $d$s are, for example, $d_{1} ...
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26 views

About multiple testing and power analysis

Doing a power analysis for a single t-test is relatively simple. What if I have to do several tests? If I were to use the Bonferroni correction, I could just take the significance level as 0.05 ...
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1answer
164 views

Can you calculate the power of a Kolmogorov-Smirnov test in R?

Is it possible to do a power analysis for a 2-sided Kolmogorov Smirnov test in R? I am testing whether two empirical distributions differ using ks.test(), and am looking to add a power analysis. I ...
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0answers
55 views

Power analysis for logistic regression

I have to deliver a statistical analysis plan that will have to be approved by an ethic commettee before I could start a clinical trial. I usually deal with different kinds of tests, whose power ...
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2answers
152 views

A priori power analysis: calculating sample size based on percentages

I'm trying to calculate the sample size, given alpha, beta resp. power, ...
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1answer
68 views

Power analysis for binomial test via simulation

Suppose a gene is mutated in 30% of the samples. I want plot the number of samples required to see 30% of them mutated at various level of power. I want to do this through a simulation so I ...
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0answers
141 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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0answers
74 views

Calculating sample size

I am going to conduct a research and would like to estimate the sample size that I will need. Here is the information that I have, please let me know if you need some more information. Thanks in ...
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1answer
121 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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1answer
45 views

Multiple regression a-priori analysis of power for sample size

I have used g-power and an online calculator to determine the sample size for a 2 factor regression but am unsure as to what effect size I desire as for a large effect size (.5) I only need 20-30 ...
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0answers
96 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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30 views

Can one manipulate data to demonstrate the power of the analysis?

I was asked this question about the demonstration of power. There are two groups of data, say control and treatment. If conducting a test( say a linear regression including other factors, but the ...
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22 views

One way between subjects ANOVA

I am planning to use a one way between subjects ANOVA to test for a difference of compassion between three different groups My question is how many participants would i need to collect data from and ...
2
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1answer
67 views

Power analysis on chi-squared test with low cell counts

I am hoping to perform a chi-square test of independence on data in a 2x2 contingency table with the following values: ...
2
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0answers
36 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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1answer
31 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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19 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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0answers
84 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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0answers
25 views

Power analysis for AB testing— multiple variants

I'd like to do an experiment that is basically an A/B test with about 10 different conditions. A single trial results in either success or failure. The null hypothesis is that all of the conditions ...
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0answers
23 views

Determining the effect size using GPower

I have three ponds and would like to know how many random samples of algae I need to collect within each pond measuring 7 response variables. I would like to see how each pond responds to the 7 ...
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0answers
88 views

Using G*Power to determine the sample size for an repeated measures ANOVA

I am currently designing an experiment that I want to analyze using an RM ANOVA. Since some of the factors are confounded I need to do multiple ANOVAS. One analysis will be for 2x2 factors (within ...
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0answers
18 views

Cluster weights in PROC GLMPOWER

I am doing power analyses in SAS using PROC GLMPOWER to solve for a total sample size (N Total). I have clustered data (Ward method), to account for variability. There are 4 clusters of varying sample ...
2
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1answer
173 views

Computing the power of Fisher's exact test in R

Suppose that I have the following 3 x 3 contingency table: ...
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1answer
199 views

How to caculate power analysis in a descriptive study

Hi I'm currently doing a dissertation, its a descriptive quantitative study. The method of data collection is a questionnaire scaled by a 10 point Likert scale. To calculate the sample population ...
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0answers
109 views

Repeated measures or two-way ANOVA, and power analysis

A sample of patients will undergo two treatments. Every patient will receive both treatments.One treatment will on the left side and the other different treatment on the right side. Repeated ...
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0answers
37 views

Retrospective power analyis of lmer for sample size

I'm an MSc student doing an assignment where I am asked to analyze and write up a report on a dataset on environmental enrichment in zebra finches. Among other things we are being asked to do a ...
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1answer
130 views

Calculating sample size of a mixed ANOVA in R (2 between, 1 within variable)?

I'm searching for a built-in function in R for calculating the required sample size (given certain power, alpha,..) of a mixed ANOVA (2 between, 1 within variable, 2x2x2 design). Does this function ...
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0answers
94 views

Post-hoc power analysis of complex sample survey data

I am working with a complex sample survey data using Stata to determine the predictors of a given dependent variable. As part of my analysis result I want to report the post-hoc power for each ...
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1answer
96 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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1answer
16 views

Prevalence estimates based on randomized sample of clinical data

This is probably one of the more straight forward questions on here but here it is: I want to use a random number generator to sample X number of charts to look for the # occurrences of Y event. So ...
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1answer
55 views

Power analyses of 5 populations of infection data (binomial data) [duplicate]

I am PhD Biologist. I have 5 populations of infected moth larvae (3 inbred, and 2 outbred). The infection in this case is spread vertically (from mother or father to offspring). Normally the virus is ...
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0answers
102 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 ...
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1answer
34 views

Matching two power signals for similarity

Below are the images of two signals that i plotted. Both the signals are from fridge belonging to different houses. Visually looking at the plot i can tell that these plots belong to fridge as they ...
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0answers
31 views

Cross correlation of two power signals

I have two devices and their power usage data. I am trying to see how co related these two devices are. i.e If i use device 1 then how often i am using device 2. It will be helpful if anyone can ...
3
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2answers
140 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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1answer
32 views

What kind of test is this?

I have a client that wants to test 3 pricing options to visitors of a website. All options are for the same product and service (no difference except pricing). Their current idea is to present all 3 ...
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0answers
29 views

Calculating n: Determining r

I have to calculate n for my research. I'm using a calculator (this one: http://www.cct.cuhk.edu.hk/stat/other/correlation.htm). α = 0.05 β = .2 r = ... I have trouble figuring out what r is. I get ...
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1answer
29 views

Where to read about how to build a sample size calculator for power analysis for a/b tests

I am wondering how to build a sample size calculator like this one. Will the intro chapters of a stats textbook cover this? I've taken a couple stats classes but I'm not sure how baseline effects and ...