Question

Listed below are time intervals (min) between eruptions of a geyser. The "recent" times are within the past few years, and the "past" times are from 1995. Does it appear that the variation of the times between eruptions has changed? Use a 0.05 significance level. Assume that the two populations are normally distributed.

77 | 86 |

90 | 91 |

91 | 93 |

76 | 96 |

57 | 62 |

101 | 87 |

62 | 89 |

90 | 92 |

69 | 84 |

92 | 95 |

84 | 86 |

81 | 96 |

Answer #1

Listed below are time intervals (min) between eruptions of a
geyser. Assume that the "recent" times are within the past few
years, the "past" times are from around 20 years ago, and that
the two samples are independent simple random samples selected from
normally distributed populations. Do not assume that the population
standard deviations are equal. Does it appear that the mean time
interval has changed? Is the conclusion affected by whether the
significance level is 0.10 or 0.01? Recent...

steps on STATCRUNCH
Listed below are time intervals (min) between eruptions of a
geyser. Assume that the "recent" times are within the past few
years, the "past" times are from around 20 years ago, and that
the two samples are independent simple random samples selected from
normally distributed populations. Do not assume that the population
standard deviations are equal. Does it appear that the mean time
interval has changed? Is the conclusion affected by whether the
significance level is 0.10...

The following are the interval times? (minutes) between
eruptions of a geyser. Detemine the five number summary and
construct a box plot from the data below.
83?84??85???87??89??90??91??92??94??97???97??98???99???104??106?109
The number 5 summary is?

Below represent scores on an exam, each entry one score for one
student
40
99
59
98
63
63
64
65
67
35
67
67
68
70
71
71
71
46
72
72
60
73
74
74
74
75
97
75
62
76
76
76
76
76
77
57
77
98
77
63
78
78
78
79
79
80
80
80
80
80
81
81
92
81
93
82
82
83
83
83
83
83
83
83
84
84
84...

TestScore
53
53
56
56
56
58
58
58
59
59
59
60
60
62
63
63
63
64
65
65
66
67
67
67
67
68
69
69
69
69
71
71
72
72
72
72
73
73
73
73
73
74
75
75
75
76
76
76
76
77
77
77
77
77
78
78
78
79
79
79
79
80
80
80
80
80
80
81
81
81
82
82
83
83
83
83
84
84
84...

Student Grades
Student
Test
Grade
1
76
62
2
84
90
3
79
68
4
88
84
5
76
58
6
66
79
7
75
73
8
94
93
9
66
65
10
92
86
11
80
53
12
87
83
13
86
49
14
63
72
15
92
87
16
75
89
17
69
81
18
92
94
19
79
78
20
60
71
21
68
84
22
71
74
23
61
74
24
68
54
25
76
97...

Using the accompanying Student Grades data, construct a scatter
chart for midterm versus final exam grades and add a linear
trendline. What is the model? If a student scores 7878 on the
midterm, what would you predict her grade on the final exam to
be?
Student
Midterm
Final Exam
1
75
64
2
85
91
3
80
68
4
88
83
5
76
60
6
67
80
7
78
74
8
95
94
9
67
61
10
93
87
11...

Since we are attempting to examine the behavior of a class of
students, the behavior of an individual (as we calculated in
objective 1) is really of little concern to us. Assuming that there
are 30 students enrolled for a typical class, use the central limit
theorem to calculate the following:
• What would be the shape of the
distribution of the average class grade of these 30 students?
• What would be the average class
average of...

Use ? to approximate σ. Use a 5% level of significance.
Data:
69
62
75
66
68
57
61
84
61
77
62
71
68
69
79
76
87
78
73
89
81
73
64
65
73
69
57
79
78
80
79
81
73
74
84
83
82
85
86
77
72
79
59
64
65
82
64
70
83
89
69
73
84
76
79
81
80
74
77
66
68
77
79
78
77

DHL recently selected a random sample of packages and weigh
them. The weights for the samples are given below.
Use Excel to develop a frequency distribution using classes
having equal widths.
Use Excel to develop a relative frequency and a cumulative
relative frequency distribution for the weights using the same
classes created in part b.
What percent of the sampled crates have weights greater than 96
pounds?
DHL
89
91
86
93
94
91
95
83
84
92
80
88...

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