Which of the following are necessary conditions to perform inference in regression?
1) The values of x should not have a correlation with the values of y.
2) The data come from a well-designed random sample or randomized experiment.
3) The actual relationship between x and y is linear.
4) The x values must have a normal distribution centered at 0
5) The values of y must have a normal distribution centered at 0
6) The distribution of the values around the regression line should have a normal distribution.