ISYE 6501 homework 3 solved

INSTRUCTIONS
• Every learner should submit his/her own homework solutions. However, you are allowed to
discuss the homework with each other (in fact, I encourage you to form groups and/or use the
forums) – but everyone must submit his/her own solution; you may not copy someone else’s
solution.
• The homework will be peer-graded. In analytics modeling, there are often lots of different
approaches that work well, and I want you to see not just your own, but also others.
• The homework grading scale reflects the fact that the primary purpose of homework is learning:
Rating Meaning Point value
(out of 100)
4 All correct (perhaps except a
few details) with a deeper
solution than expected
100
3 Most or all correct 90
2 Not correct, but a reasonable
attempt
75
1 Not correct, insufficient effort 50
0 Not submitted 0
Question 5.1
Using crime data from http://www.statsci.org/data/general/uscrime.txt (description at
http://www.statsci.org/data/general/uscrime.html), test to see whether there is an outlier in the last
column (number of crimes per 100,000 people). Is the lowest-crime city an outlier? Is the highest-crime
city an outlier? Are there others? Use the grubbs.test function in the outliers package in R.
Question 6.1
Describe a situation or problem from your job, everyday life, current events, etc., for which a Change
Detection model would be appropriate. Applying the CUSUM technique, how would you choose the
critical value and the threshold?
Question 6.2
1. Using July through October daily-high-temperature data for Atlanta for 1996 through 2015, use
a CUSUM approach to identify when unofficial summer ends (i.e., when the weather starts
cooling off) each year. You can get the data that you need from the file temps.txt or online,
for example at http://www.iweathernet.com/atlanta-weather-records or
https://www.wunderground.com/history/airport/KFTY/2015/7/1/CustomHistory.html . You can
use R if you’d like, but it’s straightforward enough that an Excel spreadsheet can easily do the
job too.
2. Use a CUSUM approach to make a judgment of whether Atlanta’s summer climate has gotten
warmer in that time (and if so, when).