custom_seed(123)
X <- runif(100, 900, 1000)
Y <- 3*X+rnorm(100, 0, 100)
# compute the variance of X
# compute the covariance of X and Y
# compute the correlation between X and Y
# compute the variance of X with cov()
cov(X, X)
# compute the covariance of X and Y
cov(X, Y)
# compute the correlation between X and Y
cor(X, Y)
test_function_result("cov", index = 1)
test_output_contains("cov(X,Y)")
test_output_contains("cov(X,Y)/(sd(X)*sd(Y))")