This preview shows pages 1–3. Sign up to view the full content.
ENGRD 2700 F10 Homework 1 Solutions
(65 points total)
1.
What fraction of the calls are cancelled?
(5 points)
To get the number of calls canceled, the students can use the filter and wipe out all
the data with precancel time 1, the answer of percentile is 883 / 15,000 = 5.9%.
There are also many other methods to get the answer, e.g. by sorting or COUNTIF
function. (there are many ways of computing this number and so long as the method
used is explained and the answer is correct, students should receive full points, 3
points for describing the working, 2 points for the percentile)
2 .
Provide a histogram for the time in seconds until cancellation for all of those calls that are
eventually cancelled. Explain why your histogram allows us to conclude that cancellation times greater
than about 840 seconds (14 minutes) can be disregarded as outliers. (No formal de_nition of outlier is
necessary.)
(6 points)
You can first copy the precancel time of canceled calls, and scale them into seconds
by *24*60*60. Then draw a histogram from these precancel time data. From the
histogram, you can see that there are very rare data with cancellation time greater
than 840s. (6 points broken down as follows: 2 points for ensuring the histogram
doesn't include the "1"s that indicate a noncancelled call. 1 point for scaling to
seconds from days. 1 point if the histogram axes are both labeled and there is a title
(0 if any of these labels are missing). 2 points for explaining their working and
reasoning)
3.
Now provide a second histogram for the time until cancellation for all those calls that are eventually
cancelled within 840 seconds (14 minutes). Based on your new histogram, what is the most common
value for the time until cancellation of a call?
(4 points)
Filter the data in question 2 to get all calls canceled within 840s and draw the
histogram. It’s easy to see that the most common value for cancellation time is
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Documentapproximately 300 seconds (5 minutes). (2 points for histogram to ensure that it does
not contain “1”s or calls with precancel time greater than 840s, 2 points for
indicating the most common values of time. Deduct a point if the time given as the
most common value is either too specific (say to the nearest second) or too broad
This is the end of the preview. Sign up
to
access the rest of the document.
 '05
 STAFF

Click to edit the document details