[R] Calculation of critical probability from lm()

[Rui Barradas]

Às 15:03 de 23/12/2024, Daniel Lobo escreveu:
> Hi,
> 
> I tried to replicate the values of critical probabilities reported
> from lm() function in R as below
> 
> ctl <- c(4.17,5.58,5.18,6.11,4.50,4.61,5.17,4.53,5.33,5.14)
> trt <- c(4.81,4.17,4.41,3.59,5.87,3.83,6.03,4.89,4.32,4.69)
> group <- gl(2,10,20, labels=c("Ctl","Trt"))
> weight <- c(ctl, trt)
> model_coed <- summary(lm(weight ~ group))[[4]]
> print(pt(abs(model_coed[, 1] / model_coed[,2]), length(ctl) - 1,
> lower.tail = F) * 2)
> ##2.795811e-09 2.640187e-01
> 
> However, this value is not matching with
> print(model_coed)
> 
> Could you please help me to understand where I made wrong in my calculation?
> 
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Hello,

Tip 1: check the value of the test statistic.

abs(model_coed[, 1] / model_coed[,2])

Tip 2: If the test stats are right, then what can possibly be wrong? How 
many parameters do you have and what is the number of observations n?

[Ans: n - 2 params == length(weight) - 2]

Hope this helps,

Rui Barradas




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