Question

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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 78 90 88 79 58 101 61 86 69 89 83 82 55 82 73 103 61

Past 88 89 93 94 65 86 84 92 87 91 89 91

Let mu1 be the recent times and let mu2 be the past times. What are the null and alternative hypotheses?

Calculate the test statistic. t-equals nothing (Round to two decimal places as needed.) Find the P-value. P-value equals nothing (Round to three decimal places as needed.) Make a conclusion about the null hypothesis and a final conclusion that addresses the original claim. Use a significance level of 0.10.

. Is the conclusion affected by whether the significance level is 0.10 or 0.01?

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...

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

Listed below are amounts of court income and salaries paid to
the town justices. All amounts are in thousands of dollars.
Construct a scatterplot, find the value of the linear correlation
coefficient r, and find the P-value using alpha equals0.05 . Is
there sufficient evidence to conclude that there is a linear
correlation between court incomes and justice salaries? Based on
the results, does it appear that justices might profit by levying
larger fines? Court Income 64.0 405.0 1567.0 1132.0...

AM -vs- PM sections of Stats - Significance test (Raw
Data, Software Required):
There are two sections of statistics, one in the afternoon (PM)
with 30 students and one in the morning (AM) with 22 students. Each
section takes the identical test. The PM section, on average,
scored higher than the AM section. The scores from each section are
given in the table below. Test the claim that the PM section did
significantly better than the AM section, i.e., is...

Listed in the data table are amounts of strontium-90 (in
millibecquerels, or mBq, per gram of calcium) in a simple random
sample of baby teeth obtained from residents in two cities. Assume
that the two samples are independent simple random samples selected
from normally distributed populations. Do not assume that the
population standard deviations are equal. Use a
0.050.05
significance level to test the claim that the mean amount of
strontium-90 from city #1 residents is greater than the mean...

AM -vs- PM sections of Stats - Significance test (Raw
Data, Software Required):
There are two sections of statistics, one in the afternoon (PM)
with 30 students and one in the morning (AM) with 22 students. Each
section takes the identical test. The PM section, on average,
scored higher than the AM section. The scores from each section are
given in the table below. Test the claim that the PM section did
significantly better than the AM section, i.e., is...

6.
Use the pulse rates in beats per minute (bpm) of a random
sample of adult females listed in the data set available below to
test the claim that the mean is less than 78 bpm. Use a 0.10
significance level.
Pulse Rate (bpm)
102
102
36
100
72
52
46
71
83
87
50
58
36
46
52
94
39
65
40
101
76
65
89
67
99
51
70
44
76
77
57
102
87
79
41
95...

The table below shows the number of hours per day 11 patients
suffered from headaches before and after 7 weeks of soft tissue
therapy. At alphaαequals=0.01,
is there enough evidence to conclude that soft tissue therapy
helps to reduce the length of time patients suffer from headaches?
Assume the samples are random and dependent, and the population is
normally distributed. Complete parts (a) through (f).
Patient Daily headache hours (before)
Daily headache hours (after)
1 3.1 2.4
2 1.8 2.2...

Researchers wondered if there was a difference between males and
females in regard to some common annoyances. They asked a random
sample of males and females, the following question: "Are you
annoyed by people who repeatedly check their mobile phones while
having an in-person conversation?" Among the
517517
males surveyed,
168168
responded "Yes"; among the
545545
females surveyed,
204204
responded "Yes." Does the evidence suggest a higher proportion
of females are annoyed by this behavior? Complete parts (a)
through (g)...

The data below give the weights in ounces of
randomly-selected bars of bath soap produced by two different
molding machines.
Weights (ounces)
Machine 1
11.4 12.4 12.1 11.8 11.8 11.7 12.3 12.0
11.8
Machine 2
13.0 12.4 12.4 12.1 12.3 12.1 12.5 12.0
12.1
The question of interest is whether these two molding
machines produce soap bars of differing average weight. The
computed test statistic was found to be -2.75. Find the approximate
P-value for the this test assuming that...

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