Question

A department of transportation’s study on driving speed and miles per gallon for midsize automobiles resulted in the following data:

**Speed (Miles per Hour)Miles per Gallon: 30 51 39 55 30
24 61 24 50 56**

**Miles per Gallon: 29 25 25 23 31 33 20 35 26
24**

Compute the sample correlation coefficient (to 2 decimals and enter negative value as negative number).

What can you conclude, based on your computation of the sample correlation coefficient?

Answer #1

x | y | x^2 | y^2 | xy | |

30 | 29 | 900 | 841 | 870 | |

51 | 25 | 2601 | 625 | 1275 | |

39 | 25 | 1521 | 625 | 975 | |

55 | 23 | 3025 | 529 | 1265 | |

30 | 31 | 900 | 961 | 930 | |

24 | 33 | 576 | 1089 | 792 | |

61 | 20 | 3721 | 400 | 1220 | |

24 | 35 | 576 | 1225 | 840 | |

50 | 26 | 2500 | 676 | 1300 | |

56 | 24 | 3136 | 576 | 1344 | |

Total | 420 | 271 | 19456 | 7547 | 10811 |

Correlation coefficient

=-0.94

**Therefore, we an conclude that , there is very strong
negative correlation between driving speed and miles per
gallon**

We can directly calculate correlation coefficient by using Excel.

Step 1) Enter data in Excel.

Step 2 ) Then use =CORREL command and select two
separate column data >> ok

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QUESTION 15
The speed x (in mph) of a car and the related average miles per
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Round all calculations to two decimal places.
none of these
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Y(x) = -.02x2 + 2.00x - 22.00
Y(x) = -.02x 2 + 1.77x - 21.54

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