6. A civil engineer wants to compare two instruments for measuring the amount of polychlorinated biphenyls (PCB s) in corn stalks. A sample of stalks is cut and crushed and two scoops of the material is taken. One is measured with the rst instrument and the other is measured with the second instrument. This whole process is repeated ve times. This results in parts per billion as follows:4lJ 'J Sample Instrument 1 Instrument 2'4 1 3 414 2 8 714 3 9 6H 4 4 3 i' 5 6 5 i' 'J a) Find a 95% condence interval for the mean difference in instrument readings assuming the differences have a normal distribution.\" b) Perform a hypothesis test and determine if there is a signicant difference in the instruments at 0t = 0.05!J 'J