Assume that the measurements came from a normal distribution. The variability of the manufacturing process is unknown means the same as the standard deviation is unknown.

Auto crank shafts. Here are measurements (in millimeters) of a critical dimension for 16 auto engine crankshafts:

224.120     224.001     224.017    223.982    223.989     223.961

223.960     224.089     223.987    223.976    223.902     223.980

224.098     224.057     223.913    223.999

The dimension is supposed to be 224 mm and the variability of the manufacturing process is unknown.  Is there evidence that the mean dimension is not 224mm?

1. The appropriate test to use is

a. T Test         

b. 1-Prop Z test          

c. Z Test          

d. Paired T test

2. The appropriate type of test to use based on the tails of the distribution

a. Left-tailed              

b. Two-tailed              

c. Right-tailed