- A machine produces metal rods used in an automobile suspensionsystem. A random sample of 12 rods is selected and the diameter ismeasured. The resulting data, in mm, are shown here:
                                                                                             Â
3.11 Â Â Â 2.88Â Â Â Â 3.08Â Â Â Â 3.01
2.84Â Â Â Â 2.86Â Â Â Â 3.04Â Â Â Â 3.09
3.08Â Â Â Â 2.89Â Â Â Â 3.12Â Â Â Â 2.98
a.        Find a two-sided95% confidence interval for the mean rod diameter. State theassumption necessary to find the confidenceinterval. Â
- Is there any evidence to indicate that mean rod diameter isdifferent from 2.95 at significance level a = 0.05? Write theappropriate hypothesis. Make required assumption(s).
- Can you make the same decision as in part b. from the result ofpart a. without testing the Hypothesis? If yes, how?
