Problem 9E

A tire manufacturer is interested in testing the fuel economy for two different tread patterns. Tires of each tread type are driven for 1000 miles on each of 18 different cars. The mileages, in mpg, are presented in the following table.

Car |
Tread A |
Tread B |

1 |
24.1 |
20.3 |

2 |
22.3 |
19.7 |

3 |
24.5 |
22.5 |

4 |
26.1 |
23.2 |

5 |
22.6 |
20.4 |

6 |
23.3 |
23.5 |

7 |
22.4 |
21.9 |

8 |
19.9 |
18.6 |

9 |
27.1 |
25.8 |

Car |
Tread A |
Tread B |

10 |
23.5 |
21.4 |

11 |
25.4 |
20.6 |

12 |
24.9 |
23.4 |

13 |
23.7 |
20.3 |

14 |
23.9 |
22.5 |

15 |
24.6 |
23.5 |

16 |
26.4 |
24.5 |

17 |
21.5 |
22.4 |

18 |
24.6 |
24.9 |

a. Find a 99% confidence interval for the mean difference in fuel economy.

b. A confidence interval based on the data in the table has width ±0.5 mpg. Is the level of this confidence interval closest to 80%, 90%, or 95%?

Finding Equations of Lines: Week 2; 8/30/17 Given the points (2,4) and (4,9) find the equation of the line connecting these two points. Start with: y=mx+b m=9-4/4-2=5/2 y=5/2x+b Fill in the Rest (2,4) OR (4,9) 4=5/2(2) + b -1=b ANSWER: y=5/2x-1 Practical Applications (slope) (#3, 5, 7, 9 – Written Homework) EX. Suppose R(x)=89x is a revenue function for selling x units of a product What is the meaning of the slope As a number, slope = 89/1 (rise/run) 89=$ 1=# units For linear functions, the slope above can be called “marginal” revenue. Additional revenue made from selling one additional unit o R(x) = 89x o 1 unit vs 2 units vs etc. o R(1) = 89 o R(2) = 178 (which make