Using R on some data and trying to see whether or not my data is heteroscedastic, I've found two implementations of the Breusch-Pagan test, [bptest][1] (package lmtest) and [ncvTest][2] (package car). However, these produce different results. What is the difference between the two? When should you choose to use one or the other?

    > model <- lm(y ~ x)
    > bp <- bptest(model)
    > bp
	studentized Breusch-Pagan test

    data:  model 
    BP = 3.3596, df = 1, p-value = 0.06681

    > ncvTest(model)
    Non-constant Variance Score Test 
    Variance formula: ~ fitted.values 
    Chisquare = 3.858704    Df = 1     p = 0.04948855 

These example shows that according to the tests, my data is in one case heteroscedastic and in the other case homoscedastic. I did find [this question here][3] so bptest might be studentized and ncvTest might not be, however, what does this mean then?

  [1]: http://www.inside-r.org/packages/cran/lmtest/docs/bptest
  [2]: http://www.inside-r.org/packages/cran/car/docs/ncvTest
  [3]: https://stats.stackexchange.com/questions/82695/what-is-the-difference-between-the-studentized-and-non-studentized-breusch-pagan