Chapter 4: Exploring Quantitative Data, Continued (Days 24-25)

Today in Stats, we continue with the next six pages in Chapter 4, "Exploring Quantitative Data." These pages cover mean and standard deviation.

One of the examples in the text is about cancelled flights from 1995-2005. There was one outlier during that stretch -- September 2001, with 20% of all flights being cancelled due to 9/11.

Last weekend we commemorated the twentieth anniversary of the September 11th attacks. I often tell my students the story of where I was on 9/11, close to the anniversary. With the date falling on the weekend, and with it fitting today's lesson perfectly, I tell my Stats students the story. I'll repeat it here (as I first posted on my original blog):

In the year 2001, I was an undergrad student at UCLA. I had just completed my second year and decided to take two classes over the summer. (These summer classes, along with my AP credits, would allow me to complete my bachelor's degree in just three years.)

Notice that since UCLA is on the quarter system, summer classes extended into September. We see that the fall semester typically begins in late August so that an entire semester is completed before Christmas (the same reason that high schools also now have an Early Start Calendar). But at quarter schools, only one quarter (not one semester) needs to be completed by winter break, and so they can afford to start later. The fall quarter at UCLA began the last week of September, and so summer classes start and end later.

Summer at UCLA was divided into two halves, called "A Session" and "C Session." Each session was six weeks. (Officially, "B Session" refers to a few special one- or two-week seminars only in certain departments, such as art.)

If you check the UCLA website nowadays, you'll see that math courses could be offered either A Session or C Session. But back in 2001, summer math courses were eight weeks long -- the six weeks of A Session plus the first two weeks of C Session. The class I took in Summer 2001 was MATH 132, Complex Analysis. (I still have a copy of a test I took that summer -- a perfect 300/300 score.)

The second course I took that summer was Geography 5, "People and Earth's Ecosystems," which I used to fulfill my general ed requirements. This was a C Session course that met twice a week, on Tuesdays and Thursdays. So by September, I had finished Complex Analysis, but was still attending the Geography 5 course.

Meanwhile, during my years at UCLA, I earned money by working part-time at the library. During the summer, we worked a fixed schedule for A Session and C Session. Since my math and geography classes overlapped for the first two weeks of C Session, my library hours for that session would have to accommodate both classes. If I recall correctly, my schedule was like 8-10 for Geography 5, then noon-2 for math, and afterwards I worked at the library from 2-6. Once the first two weeks of C Session had passed, I was left with a long gap between geography class ending at 10 and work not starting until 2 for the final four weeks.

September 11th, 2001 fell on a Tuesday -- and just like this year, it's the sixth and final week of C Session. And so I had to wake up early for Geography 5. I commuted a long distance to UCLA back then -- I woke up around 5-something in order to leave by 6-something.

When I first turned on the news that morning, I heard that a plane had struck one of the Twin Towers in New York City. Originally, I assumed that it was an accident. I took an early morning shower -- and by the time I came out of the shower, a second plane had hit the other tower. I knew that the probability of two planes having accidents about a half-hour apart, with each plane hitting the World Trade Center, was infinitesimal. The plane crashes were clearly intentional!

I began the long commute to UCLA. On the way there, I hear about the events of the East Coast on the radio. I reach the campus in time for my 8:00 Geography 5 class. I arrived expecting a long lecture followed by review for the final -- to be held two days later, on Thursday.

As the title of the class implies, the subject material of the class is all about what effect humans have on the planet and its ecosystems -- indeed, how we cause the ecosystems to change over time. And so this is what the professor said to open the class:

"This summer, we've learned how the world can change over a period of many years. But today, we see that the world can change a whole lot in a single day."

He dropped the lecture format for that day, and instead allowed the class to discuss what was happening in New York. Some students had grown up on the East Coast, and they were undoubtedly fearful of what was going on. Not until the last few minutes of class did the professor remind us of what would be on Thursday's final.

Class ended, and it was time for my long break between class and work. I walked to the library (the same one where I worked) and studied a little for Thursday's final. Then I went to the computers and decided to play around on the Internet. It was only then when I realized exactly how much the world had changed that day.

You see, there was a huge bank of computers on the first floor of the library. But on the second floor, there was a lone computer in walking distance of a restroom. I knew about the computer mainly because I worked there -- so most of the time this computer was open. Because of its proximity to the restroom, I liked to use that computer. Yet I was afraid that by the time I'd return from the restroom, someone would take that computer. So I had a bright idea -- I'd leave a window open on some website and leave my backpack behind as I went to the restroom. Hopefully, other patrons would get the hint that the computer was taken.

When I returned from the restroom, a security guard was standing at the computer waiting for me. He asked me, "Is that your backpack over there?" When I nodded, he continued, "Someone had called in a bomb threat, so we had to make sure that it was yours."

I knew that the "bomb threat" was the general events occurring on the East Coast. In other words, because it was 9/11, the security guards were afraid that my backpack contained a bomb and that I'd walked away before it exploded. Only then did I know that the world had changed -- and it was a world full of fear, uncertainty, and doubt.

After the encounter with the security guard, I was no longer in the mood to use the computer. It was approaching lunch time anyway, and so I left the library and walked to the student union. As I ate, I saw the news continue to cover the events of New York -- and Washington DC. I recall reading the scroll bar on the bottom of the TV -- all sporting events had been cancelled, not just the games in the two cities that had been attacked.

I thought about the people -- the people on the planes, the people in the towers. I began to shed tears for all of the victims.

When it was time for work, I returned to the library. It goes without saying that my boss and student coworkers were discussing the tragic events. After work, I took the long walk back to the car. I glanced at the TV in the student union along the way and saw burning buildings on the screen -- and I was afraid that downtown LA had been attacked as well. It wasn't until I listened to the radio along the drive home that I learned that the West Coast had been spared after all.

On Thursday, September 13th, I took the Geography 5 final and passed the class. During the long break between class and work, a group of students were gathering in front of Royce Hall. A moment of silence was held for all the victims who had died two days earlier -- just as a moment of silence is held at the school where I sub at today.

And that's my answer to the question, "Where was I on 9/11?"