In a large study of compact cars, the average (mean) miles per gallon (mpg) is 2

Question

In a large study of compact cars, the average (mean) miles per gallon (mpg) is 28, with a standard deviation of 3 mpg. Assume the histogram for these cars mpg approximately follows the normal curve. Using this information, answer the next 3 questions 3. Approximate the percentage of compact cars that will get over 30 mpg a. 0.2514 b. 0.3300 c. 0.6700 d. 0.7486 4. Approximate the percentage of compact cars that get less than 20 mpg a.0.9962 h-0.0038 c. 0.0038 d. 2.67 s. What value (mpg) represents the 90th percentile for compact cars mpg? a. 30.7 b. 30.4 c. 31.8 d. 28.3

Explanation / Answer

3.The percentage of compact cars that will get over 30 is
P(X>30) = P(Z > (30-28)/3)) = P(Z>0.6667) = 0.25249 = 25.249%

4. The percentage of comapct cars that get less than 20 is
P(X<20) = P(Z< (20-28)/3)) = P(Z<-2.6667) = 0.00383 = 0.383%

5. The percentage of 90th percentile for compact cars is
X = 28 + Z90% 3 = 28 + 1.645*3 =0.32965 = 32.935%

Related Questions

Navigate

• Browse (All)
• Browse I
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.