Sample size calculation for logistic regression when the independent variable is binary

Sample size calculation for logistic regression when the independent variable is binary. The calculation is made using the free software G*Power and an example where the independent variable is gender. The dependent variable is if the patient got an antibiotic prescription or not. More information about sample size calculations is found at: science-network.tv/sample-size...

[@chien533]

Very helpful, but how to set up the distribution of a categorical independent variable with more than 2 levels?

[@withrosesinhair123]

That was a strangely sexy intro, given the topic.

[@davidrover3487]

Hey, thank you for the video, that did help a lot. But I've got a question. How can you do this, when you have an withing-subject-design. My dependent variable is the correct solution of a task (2 conditions: yes/no) and every participant goes through all conditions of the independet variable

[@iancg1]

How do you calculate the X parm input parameter?

[@dr.dharmarampoonia7942]

Excellent.

[@heavenlyblessed2044]

Thank you! Please make a video sample size calculation for logistic regression when the independent variable is continuous.

[@science-network]

That is on my to do list. Sorry for the inconvenience.

[@eduardprades5350]

Thank you!!

[@aisyahaisyah3494]

You are a life saver! In this video u did mention about continuous variable, do you have other video for that?

[@science-network]

That is on my to do list. Sorry for the inconvenience.

[@kevenjune3904]

How to calculate R^2 when you have other covariates?

[@ronny-gunnarsson]

You don't calculate sample size to achieve a specific R^2. R^2 is relevant when you calculate sample size for multivariate regression such as logistic regression. You may find some guidance about this here: science-network.tv/sample-size-estimation/#Sample_size_calculation_in_multivariate_regression

[@science-network]

The video about continuous variables is still under construction. For other information around sample size calculation please have a look at: science-network.tv/sample-size-estimation/

[@lynni1823]

Do you have a video for a continuous predictor?

[@science-network]

That is on my to do list. Sorry for the inconvenience.

[@lynni1823]

@@science-network Thanks for your reply! Similar to how you explained how to obtain the probabilities used in the above method (e.g., assumptions made based on previous publications), it would be great if you could include a similar explanation for how we should determine the probabilities used for the continuous predictor method. Thanks!

[@balasiddu]

How to compute sample size when age and gender variable interacts?

[@science-network]

Considering interaction between variables in a sample size calculation is complex and most researchers would ignore this when calculating sample size. If you want to dig into this have a look at this: journals.plos.org/plosone/article?id=10.1371/journal.pone.0207745 (sorry but I can't help you further with this).

[@balasiddu]

@@science-network Thanks I shall have a look into it.