U test on average resistance. The resistance of a resistor from a manufacturer is Gaussian distributed N (, 2) with = 2000 and = 7. A new production line was recently put in use. It seems from observations that the tolerance in the resistance (i.e., ) has not changed but the resistance may have a bias (i.e., = 2000 might be untrue). The following sample was then obtained

1997, 1986, 1987, 1995, 2015, 2005, 1997, 1996, 2011, 2007, 2004, 2003, 2004, 2012, 1993 Can we say that the average resistance has changed with 95% confidence?