Buoi1(1)

# Bai 1: tinh trung binh so duong
x <- rnorm(100)
x[x < 0] <- NA
tb <- mean(x, na.rm = TRUE)
tb

## [1] 0.7948793

# Bai 2: Can bac hai cua trung binh sai so binh phuong
df <- data.frame(
  t = c(3, 5, 2, 7),
  y = c(2.5, 5.5, 2, 8)
)

error <- df$t - df$y
binhphuong <- error^2
mse <- mean(binhphuong)
rmse <- sqrt(mse)
rmse

## [1] 0.6123724