Suppose you want to model the stopping distances of cars ( dist ) based on their speed ( speed ). Your task is to test for the presence of outliers in the data using Grubbs' test .
library(outliers)

data("cars")

head(cars) Use the grubbs.test function from
the outliers package and select the correct answer .

Question

Suppose you want to model the stopping distances of cars ( dist ) based on their speed ( speed ). Your task is to test for the presence of outliers in the data using  Grubbs' test . 
  library(outliers)  
 
data("cars") 
 
head(cars)  Use the  grubbs.test  function from
the  outliers  package and  select the correct answer .

Accepted Answer

There are  no significant outlier s  present in either variable
at a  1% significance level .

Answer

The lowest value of  spee d  (4) and the highest value of  dist 
(120)  a re  significant outliers .

Answer

There is no strict rule to decide, but  some literature sugges ts  that points for which Grubbs’s value is higher than 1 should be considered as outliers. Other literature provides a threshold of 4/n or 4/(n−k−1).

Answer

At a  5% significance
level , the variable  speed  includes at least one outlier, while  dist  does not.

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