1. Here are the salaries of 24 IT professionals in 2009 in Chicago:
$109,000 $ 65,000 $65,000 $ 59,000 $ 180,000 $ 101,325 $ 130,000
$95,000 $ 81,500 $69,000 $71,500 $ 74,880 $64,000 $72,000
$ 71,000 $ 82,300 $49,000 $51,200 $ 39,000 $48,500 $64,330
$ 41,100 $52,330 $82,000
a. Make a frequency distribution using five classes with the upper class limit of the first class as the
lower class limit of the second.
b. Make a histogram from your frequency distribution.
2. Find the prices of 10 different printers for your PC. Compute the mean, median and mode of
3. In the following table you can see the Memory Usage at a given moment of a PC computer.
a. Find the measures of tendency and the measures of dispersion of the memory usage in Kb.
b. Once you complete the computation of the measures, complete a scatter plot of those values.
c. Identify the values that are responsible for the variance of the dataset, give a possible solution on
how the computer user could decrease his Memory usage variance.
4. There is a mathematical theory called queuing theory that studies ways in which computer jobs
are fed in CPUs and researches on how these can be reduced to a minimum. Show how can a
computer estimate the average number of jobs waiting at a queue?
Suppose that in a 5 sec interval jobs arrive as indicated in the following table ( Arrival time is
assumed to be at the beginning of each second) In the first second jobs A and B arrive. During
the second second B moves to the head of the line ( A job is completed as it took 1 sec to be
served), and C and D jobs arrive and so on.
a. The mean number of jobs in line
b. The mode of the number of jobs in line
Time in seconds Jobs
5. Many times, we are required to use statistical measures to try and construct a problem.
We run a program for a 10 different inputs. The times are measures in 1-second intervals and none of
them took 0 secs.
a. Suppose the standard deviation of a set of times we run the program is 0. What does this tell
you about the running times?
b. Suppose that the mean of the times is 1000.9 sec while the median is 1 sec. Explain what do you
know about the program running times for all 10 different inputs?
c. Assume now that the mean of the times is 1000.9 sec while the median is 1 sec and the
variance is 9998000. Explain what do you know about the program running times for all 10
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