Linked Questions

1
vote
0answers
677 views

Power Analysis for Logistic Regression with one nominal variable [duplicate]

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?
3
votes
2answers
174 views

Power analysis for logistic regression with dummy independent variables [duplicate]

Per reviewer request, I need to do power analysis for a logistic regression model with multiple dummy variables. I have four groups: Control, (Treatment) A, B, and C. The hypothesis is that group A ...
2
votes
0answers
177 views

Power analysis for logistic regression [duplicate]

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 ...
1
vote
1answer
90 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 ...
299
votes
10answers
287k views

Difference between logit and probit models

What is the difference between Logit and Probit model? I'm more interested here in knowing when to use logistic regression, and when to use Probit. If there is any literature which defines it using ...
34
votes
3answers
37k views

Significance contradiction in linear regression: significant t-test for a coefficient vs non-significant overall F-statistic

I'm fitting a multiple linear regression model between 4 categorical variables (with 4 levels each) and a numerical output. My dataset has 43 observations. Regression gives me the following $p$-...
22
votes
1answer
16k views

Calculating statistical power

As I understand it, I need to know at least three aspects (out of four) of my proposed study in order to conduct power analysis, namely: type of test - I intend to use Pearson's r and ANCOVA/...
12
votes
4answers
7k views

Power analysis for ordinal logistic regression

I am looking for a program (in R or SAS or standalone, if free or low cost) that will do power analysis for ordinal logistic regression.
81
votes
0answers
64k views

How can a regression be significant yet all predictors be non-significant? [duplicate]

My multiple regression analysis model has a statistically significant F value however all beta values are statistically non-significant. All the regression assumptions are met. No multicollinearity ...
4
votes
3answers
3k views

Experiment or simulation to undestand type I and type II errors

I am studying Type I and Type II errors and basic concepts of testing hypotheses. To better develop my intuition I would like to write a few simple simulations. What I'm hoping is to get a base ...
3
votes
2answers
14k 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 ...
6
votes
2answers
945 views

Power for experimental design

It's easy to calculate power for paired t-tests and ANOVA, but how do you calculate power for more complicated designs such as split plot designs or factorial designs?
4
votes
1answer
4k views

Computing the power of Fisher's exact test in R

Suppose that I have the following 3 x 3 contingency table: ...
4
votes
3answers
6k 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 ...
5
votes
1answer
2k views

Simulate data for power analysis of logistic regression model - include covariance variance of variables?

I've tried to simulate data for a power analysis of a logistic regression. The results of the power analysis look reasonable: power=90% for a sample of 6000 persons. But I feel that the analysis lacks ...

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