Refer to Buena School District bus data. Prepare a report on the maintance cost

Question

Refer to Buena School District bus data. Prepare a report on the maintance cost for last month. Be sure to answer the following questions in your report.

A. Around what values do the data tend to cluster? Specially what was the mean maintenance cost last month? What is the median cost? Is one measure more representative of the typical cost of others?

B. What is the range of the maintenance costs? What is the standard deviation? About 95% of the maintenance costs are between what two values?

http://highered.mheducation.com/sites/0078020522/student_view0/data_sets.html (for all data)

Maintenance cumulative lower upper midpoint width frequency percent      frequency percent 320 < 340 330 20 3   3.8   3   3.8   340 < 360 350 20 3   3.8   6   7.5   360 < 380 370 20 1   1.3   7   8.8   380 < 400 390 20 8   10.0   15   18.8   400 < 420 410 20 5   6.3   20   25.0   420 < 440 430 20 12   15.0   32   40.0   440 < 460 450 20 12   15.0   44   55.0   460 < 480 470 20 15   18.8   59   73.8   480 < 500 490 20 7   8.8   66   82.5   500 < 520 510 20 8   10.0   74   92.5   520 < 540 530 20 1   1.3   75   93.8   540 < 560 550 20 3   3.8   78   97.5   560 < 580 570 20 2   2.5   80   100.0   Descriptive statistics Maintenance count 80 mean 450.29 sample variance 2,882.18 sample standard deviation 53.69 minimum 329 maximum 570 range 241 1st quartile 420.00 median 456.00 3rd quartile 489.75 interquartile range 69.75 mode 329.00 low extremes 0 low outliers 0 high outliers 0 high extremes 0

Explanation / Answer

Sol:

A:

mean  maintenance cost last month=$450.29

median  maintenance cost last month=$456

median is best measure as it is not affected by outliers

SolutionB:

range of maintenance cost =$241

std deviation=s=$53.69

95% of the maintenance costs are between what two values

=mean-z(stddeviation/sqrt(samplesize) and mean-z(stddeviation/sqrt(samplesize)

z for 95%=1.96

sample size=n=count=80(given from data)

=450.29-1.96(53.69/sqrt(80),450.29+1.96(53.69/sqrt(80),

=438.52 and 462.06

lower limit=$438.52

upper limit=$463.06

95% of the maintenance costs are between $438.52 and $463.06

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