1
$\begingroup$

I need to calculate the centile curve for y using a GAMLSS model with age and height as predictors. The plots below depict the relationship between log(y) and each of the independent variables.

enter image description here

enter image description here

I incorporated log of age and log of height into the model to make the relationship between these variables more linear. The findings reveal that age does not influence all factors.The R2=0.8 and RMSE=0.3. Do you recommend me to remove sigma.fo =~pb(log(Ph1_Alter_2)) from the model and put sigma.fo =~1? Is it necessary for age and height to be significant for all parameters when the goal of a project is centile estimation?

m8 <- gamlss(y ~ log(Ph1_Groesse) + pb(log(Ph1_Alter_2)), sigma.fo =~pb(log(Ph1_Alter_2)), nu.fo =~1, family = BCCGo(mu.link = "log"), data=DAT1.F)

enter image description here

Improve this question
$\endgroup$

1 Answer 1

Reset to default
0
$\begingroup$

The p-value 0.2768 is just for the linear term in log(Ph1_Alter_2), and does not tell you if the smoothing term is significant.

There is good example of centile estimation for Y based on 2 X variables in Rigby et al. (2019) Section 5.9, pages 100-108

NOTE:

The p-value after pb(log(Alter_age)) in the output is the significance of the LINEAR term in log(Alter_age).

It is NOT the significance of the whole nonlinear smooth pb term.

Improve this answer
$\endgroup$
2
  • $\begingroup$ thanks for your time. I am confused. The p-value of pb(log(Alter_age)) is not significant. And pb refers to the nonlinear trend which is smoothing term. Please correct me if I am not right? – $\endgroup$
    – stats
    Commented Jan 27, 2023 at 14:53
  • $\begingroup$ thanks for the reply. Do you recommend to consider sigma.fo =~1 as pb(log(Alter_age)) is not significant? $\endgroup$
    – stats
    Commented Jan 27, 2023 at 21:32

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.