Question

Provided in the date below a set of restoration times for 35 failed power transformers. The data were collected for recent transformer failures by a fairly novice work crew. a. What is a 90% confidence interval for mean restoration time? b. What is a 99% confidence interval for mean restoration time? c. If the industry standard for such a restoration is 2.7 hours, discuss how well the work crew in this analysis performed.

2.2 |

1.7 |

2.4 |

2.5 |

2.9 |

4.4 |

5.1 |

1.8 |

3.2 |

2.2 |

1.9 |

4.4 |

5.2 |

5.6 |

2.5 |

4.5 |

3.7 |

4.3 |

4.3 |

2.4 |

3.6 |

2.5 |

1.9 |

2.7 |

4.5 |

3.3 |

3.9 |

2.7 |

3.8 |

3.9 |

3.3 |

2.1 |

1.6 |

1.5 |

2.9 |

Answer #1

A)

sample mean, xbar = 3.18

sample standard deviation, s = 1.131

sample size, n = 35

degrees of freedom, df = n - 1 = 34

Given CI level is 90%, hence α = 1 - 0.9 = 0.1

α/2 = 0.1/2 = 0.05, tc = t(α/2, df) = 1.691

CI = (xbar - tc * s/sqrt(n) , xbar + tc * s/sqrt(n))

CI = (3.18 - 1.691 * 1.131/sqrt(35) , 3.18 + 1.691 *
1.131/sqrt(35))

CI = (2.86 , 3.5)

B)

Given CI level is 99%, hence α = 1 - 0.99 = 0.01

α/2 = 0.01/2 = 0.005, tc = t(α/2, df) = 2.728

CI = (xbar - tc * s/sqrt(n) , xbar + tc * s/sqrt(n))

CI = (3.18 - 2.728 * 1.131/sqrt(35) , 3.18 + 2.728 *
1.131/sqrt(35))

CI = (2.66 , 3.7)

C)

For 90% CI, the value of 2.7 is below the lower limit of the
calculated CI. Hence crew worked below the industry standard.

For 99% CI, the valeu of 2.7 is included in the CI. Hence crew worked as per the industry standard.

Listed in the accompanying data table are student evaluation
ratings of courses and professors, where a rating of 5 is for
"excellent." Assume that each sample is a simple random sample
obtained from a population with a normal distribution.
a. Use the 93 course evaluations to construct a 98%
confidence interval estimate of the standard deviation of the
population from which the sample was obtained.
b. Repeat part (a) using the 93 professor
evaluations.
c. Compare the results from part...

Data shows the times for carrying out a blood test at
Rivervalley Labs
Using Excel Plot a histogram of the data. What type of
distribution does the data appear to follow?
Construct and interpret the 95% confidence interval for the
population mean time for carrying out a blood test. Assume that the
population standard deviation is unknown.
Times for blood tests (minutes)
2.5
4.9
3.6
4.3
1.9
3.4
3.2
4.0
3.1
3.6
3.9
4.4
3.9
3.1
2.7
3.5
3.6
3.7...

Build a stem-and-leaf plot for these measurements
3.1
4.9
2.8
3.6
2.5
4.5
3.5
3.7
4.1
4.9
2.9
2.1
3.5
4.0
3.7
2.7
4.0
4.4
3.7
4.2
3.8
6.2
2.5
2.9
2.8
5.1
1.8
5.6
2.2
3.4
2.5
3.6
5.1
4.8
1.6
3.6
6.1
4.7
3.9
3.9
4.3
5.7
3.7
4.6
4.0
5.6
4.9
4.2
3.1
3.9
A. Describe the form of data distribution. Do you notice any
unusual results?
B. Use the stem-and-leaf plot to find the minimum
observation....

Use the data in Bank Dataset to answer this question.
Construct a 95% confidence interval for the mean increase in
deposits. Note that the population standard deviation σ is not
known in this case. Instead the sample standard deviation s should
be calculated from the sample and the t distribution should be
used.
2. What is the margin of error at the 95% confidence level?
Bank Dataset of Increase in deposits. Mean is 4. Sample size is
152 customers.
4.3...

We wish to determine the impact of Specification Buying, X11, on
Satisfaction Level, X10. To do so we will split the Hatco data file
into two separate data sets based on the Specification Buying, X11.
This variable has two categories:
1=employs total value analysis approach, evaluating each
purchase separately;
0 = use of specification buying.
Sort the entire Hatco data set based on Specification Buying.
This will create two separate groups of records. Those records with
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Year-Year Percent Change in Commodities CPI
Year-Year Percent Change in Services CPI
Year
Commodities%
Services%
1960
0.9
3.4
1961
0.6
1.7
1962
0.9
2.0
1963
0.9
2.0
1964
1.2
2.0
1965
1.1
2.3
1966
2.6
3.8
1967
1.9
4.3
1968
3.5
5.2
1969
4.7
6.9
1970
4.5
8.0
1971
3.6
5.7
1972
3.0
3.8
1973
7.4
4.4
1974
11.9
9.2
1975
8.8
9.6
1976
4.3
8.3
1977
5.8
7.7
1978
7.2
8.6
1979
11.3
11.0
1980
12.3
15.4
1981
8.4...

7. Using Excel, find the mean and the standard deviation of the
AT&T speeds from the data set #32 Airport Data Speeds. Round
your answers to 3 decimal places. (Show your work!)
mean, x :
standard deviation:
AIRPORT
CODE
VERIZON
SPRINT
AT&T
T-MOBILE
ATL
77.8
0.4
33.9
27.3
AUS
28.5
0.5
29.0
5.1
BNA
1.9
2.3
4.6
9.5
BOS
6.2
1.0
11.7
9.6
BWI
43.0
3.4
12.7
3.2
CLE
15.1
0.5
7.6
24.7
CLT
7.9
1.1
9.1
4.4
CMH
25.7...

Year
Unemployment rate
gdp growth
cpi
inflation rate
1980
7.2
-0.2
87
1981
7.6
2.6
94
8.05
1982
9.7
-1.9
97.6
3.83
1983
9.6
4.6
101.3
3.79
1984
7.5
7.3
105.3
3.95
1985
7.2
4.2
109.3
3.80
1986
7.0
3.5
110.5
1.10
1987
6.2
3.5
115.4
4.43
1988
5.5
4.2
120.5
4.42
1989
5.3
3.7
126.1
4.65
1990
5.6
1.9
133.8
6.11
1991
6.9
-0.1
137.9
3.06
1992
7.5
3.6
141.9
2.90
1993
6.9
2.7
145.8
2.75
1994
6.1
4.0...

To measure profitability, La Quinta used operating
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In R, if I have a plot of LIFE against BIRTH and I want to
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manually referring to this value as other state can have the same
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