Harley-Davidson Stock Volume The trade volume of a stock is the number of shares traded on a given day. The following data, in millions (so that 2.45 represents 2,450,000 shares traded), represent the volume of Harley-Davidson stock traded for a random sample of 40 trading days in 2010.

2.45 |
2.10 |
7.11 |
2.91 |
1.92 |
1.45 |
2.31 |
1.41 |

1.62 |
4.48 |
2.30 |
1.42 |
3.26 |
2.82 |
1.66 |
2.30 |

1.58 |
1.91 |
1.67 |
2.66 |
1.47 |
1.14 |
3.06 |
3.09 |

2.83 |
1.77 |
1.50 |
6.19 |
2.84 |
1.94 |
2.02 |
1.71 |

1.87 |
1.83 |
2.03 |
2.62 |
1.81 |
1.89 |
1.64 |
0.89 |

(a) Use the data to compute a point estimate for the population mean number of shares traded per day in 2010.

(b) Construct a 90% confidence interval for the population mean number of shares traded per day in 2010. Interpret the confidence interval.

(c) A second random sample of 40 days in 2010 resulted in the data shown next. Construct another 90% confidence interval for the population mean number of shares traded per day in 2010. Interpret the confidence interval.

2.07 |
2.39 |
1.24 |
2.02 |
2.23 |
1.67 |
2.06 |
2.74 |

5.19 |
2.38 |
3.32 |
2.44 |
2.34 |
2.74 |
1.37 |
1.60 |

1.71 |
1.64 |
2.20 |
1.43 |
1.48 |
2.05 |
3.75 |
3.30 |

2.70 |
2.44 |
1.67 |
1.38 |
3.12 |
1.69 |
1.79 |
2.05 |

3.59 |
1.79 |
2.20 |
1.54 |
0.84 |
2.19 |
1.69 |
1.77 |

(d) Explain why the confidence intervals obtained in parts (b) and (c) are different.