STR <- c(23, 19, 30, 22, 23, 29, 35, 36, 33, 25) TS <- c(430, 430, 333, 410, 390, 377, 325, 310, 328, 375) mod <- lm(TS ~ STR) # compute 90% confidence intervals for the model coefficients confint(mod, level = 0.9) test_function("confint", args = c("object", "level"))