# Search results

1. ### Can I set the breakpoint of piecewise regression by theoritic reference?

Thank you karabiner. You might set quadratic term of BMI for the non-linearity. But do I need to add interaction term of b5*(year*BMI^2) ? Or use b5*(year*BMI^2) instead of b4(year*BMI)?
2. ### Can I set the breakpoint of piecewise regression by theoritic reference?

This is my result. In this table I didn't perform piecewise regression. Instead of pieciwise regression, I performed 40 (8*5) simple linear regression (SBP on BMI) for all combination of year * BMIgroup. I thought direct comparison of these coefficient is not statistical , because each group is...
3. ### Can I set the breakpoint of piecewise regression by theoritic reference?

Thank you for your reply. I have SBP&BMI data for 6 years. I want to show SBP & BMI relationship increase when BMI category is increasing. In addition, want to show yearly increasing SBP& BMI relationship in each BMI category. Then is there any appropriate way of analysis that shows above?
4. ### Can I set the breakpoint of piecewise regression by theoritic reference?

I want to prove different regression coefficient for SBP on BMI according to BMI categories. So I want to use piecewise regression. BMI is categorized by WHO guideline which means medicaly proven breakpoint. (<18.5 , 18.5-23, 23-25, 25-30, >30) Can I use these breakpoint ? Or do I have to...
5. ### Is there proper homoskedasticity test for large sample size data ??

But too many observation disturbs visualization. Is there anyother test for the homoskedasticity? Or F ratio reference for the large sample size
6. ### Is there proper homoskedasticity test for large sample size data ??

Hi I want to perform ANOVA. So have to check homoskedasticity and normality. I know that Levene's test has type 2 error for the large sample size. Is there proper homoskedasticity test for large sample size data ? I found hartley's F ratio, but which only gives limited information to the 60...
7. ### Question about interaction in regression

Than you for reply. I used gam package in R , selecting the df 4 , and in multivariable model. logitgam1<-gam(upro ~ s(bmi,df=4)+ s(sbp,df=4)+ s(dbp,df=4)+ s(gfr,df=4), data=bp, family=binomial) summary(logitgam1) plot(logitgam1,se=T) I also tried to draw logit(proteinuria) & sbp graph with...
8. ### Question about interaction in regression

My assumption was, SBP shows something nonlinear relationship with outcome than linear. I just choose quintile for the purpose easy interpretation of the result . Quintile shows more flexible change of odds ratio than quartile, tertile. I could choice the regression which dealing with nonlinear...
9. ### Linearity assumption for logistic regression (very simple question plz help me)

For example, If at age 20, total 100 observation, 50 event and 50 non-event Log(0.5/0.5) would be real logodds of age20 If At age 30, total 100 observation, 10 event and 90 non-event Log(0.1/0.9) would be real logodds of age30 If At age 40, total 100 observation, 70 event and 30 nonevent...
10. ### Linearity assumption for logistic regression (very simple question plz help me)

Hi. Do I have to check linearity assumption of logistic regression (Log odds of outcome with continuous variable) using graph of predicted logodds (by logistic regression) and continuous variable Or using graph with real logodds and continuous variable ? I think the latter is right. In...
11. ### Question about interaction in regression

Thank you for your reply. In article dealing with aneurysm, they recommend theoretic or clinical cut-point instead of data-driven cut-points. If I choose the clinically used cut off levels of 120 and 140 (<120,120-140, >140), would there be any problems with catgorical variables? Or do I...
12. ### Question about interaction in regression

To hlsmith Thank you for reply 1) outcome variable is prevalence of proteinuria. cross sectional study, same age, male, 300,000 observations. 2) I checked linearity between logit & continuous variable by visualizing using Generalized additive model. below is graph of SBP, DBP, BMI with...
13. ### Question about interaction in regression

It's my first time to write here to ask question. Please, if someone know any clue for my problem, help me. I'm running logistic regression for outcome on SBP(systolic blood pressure), DBP(diastolic blood pressure), BMI , and other covariates. Because SBP, BMI didn't show linear relationship...