Synthetic oils. Synthetic oils are oils formulated with the base oil coming from an advanced chemical industry. It may reduce friction and help engines live longer. Mobil 1 synthetic oil is engineered to be more robust in terms of low-temperature pumpability, high-temperature stability, and protection against deposits. A test has been conducted to test cars’ engine temperature stability (in 0F) with the Mobil 1 synthetic oil. Two groups of the same type of cars were selected, with the first group being without the Mobil 1 synthetic oil and the second group being with the Mobil 1 synthetic oil. Here are two possible tests to study the question of whether the Mobil 1 synthetic oil may or may not stabilize the car engine temperature.

Paired t-Test of m11 - 22 Mean of Paired Differences = 50 t-Statistic = 2.481 w 7 20 dfp = 0.0111 2-Sample t-test of m1 - m2 Difference Between Means = 53 t-Statistic = 1.733w 7 27 dfp = 0.0473

a) Which of these tests is appropriate for these data? Explain.

b) Use your selected test and state your conclusion.