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I am using Cox proportional hazard regression to determine the association between physical behaviors (physical activity, sedentary behavior, and sleep) and mortality. to elaborate on these results, I have created hypothetical combinations for physical behaviors to see how they are related to mortality. for example, what happens to probability of dying if physical activity is increased by 1 hour and sleep is decreased by 1 hour while keeping the sedentary time constant. doing this step, I got survival probability for each new hypothetical combination of physical behaviors for each time point during follow-up.

my question is how to calculate hazard ratio from survival probabilities obtained at each time point in r?

also, we get probabilities at each time point of follow-up, how to get that one number on hazard ratio that researchers report in the article based on these probabilities?

After this,

i also want to calculate how much is the difference between probabilities obtained based on new combination and reference combination (average physical behaviors where we did not change anything in the physical behaviors). this step will tell me the effect size due to a hypothetical change in physical behaviors.

after this, I want to know if these difference in probabilities is significant.

any suggestion on how can I calculate the difference between survival probabilities and the confidence interval of this difference at each time point?

I am desperate for help.

Regards N

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