From Maura:
My class did not do as well on the exam as I thought they would. On the other hand, most of them finished the exam during the exam time. We talked a bit about writing complete answers, showing work, etc. I told them that I thought it would get better, but that they also needed to keep practicing.
Then we started Chapter 6, looking at the Wing Aero data. We opened up the table in Excel and spent some time making sure we understood the information in the table. The chart shows salaries for four different groups of employees. I showed them how to sort the salary data and what to do with that information: put it in a sentence that gives it a context. In this case, the largest salary is more than 15 times the lowest salary. Then we used Excel to do some tedious work. We summed the salaries to get the total payroll, we counted the number of workers in each category using the COUNT function (and found out that it works on numbers but not on “general” entries) and then we made Excel calculate the mean by dividing. It was a lot of steps and I told them that we’re doing this in part to see some of what Excel can do. Then we used the AVERAGE function in Excel and found to our relief that we had the same answer.
I then told them that the advantage of using Excel (or something like it) is that we don’t get distracted by the calculation. Instead, we can use our brain power to talk about what it means. So I asked a student, “would you work for this company if they told you that the average salary was $77,000?” Responses varied, but they thought it looked pretty good. Then we looked at the data again and realized that most people in the company earned less than $77,000. We calculated the median and found that it was $42,500. In this case, a much better representation of the salaries. Would you work for the company if they told you the average salary was $42,500? Some people would.
To give them a real contrast between mean and median I drew a city block on the board with four residences: one person earned $30,000, one $40,000, another $30,000 and Bill Gates earned $5 billion. We calculated the mean (why not use Excel, now that it’s there?) and the median. The median is just $35,000 while the mean was $1.25 billion. It’s absurd but it tells us how the outliers could really skew the mean. And it points out the challenges of trying to summarize a bunch of data with one number. At this point one student groaned and said it all sounded like what she had done in Statistics, a course that apparently she didn’t like much. I asked why not, and she said that it was just a bunch of formulas and math. Again, I told them that we are using Excel so that we don’t have to worry about the formulas or the calculations. We do have to pay attention to what we ask Excel to do, of course, but our main work lies in understanding and interpreting the answer. I told them that this is what I think is fun, but their response was basically that of course I think it’s fun, since I like teaching math. I hope that by the end of the semester they’ll have some fun with it too.
In the last bit of class time (never a good idea) we built a column graph. It took awhile, as first we had to sum up the salaries in each category and also count the number of workers in each category. We’ll have to review that next time and go on to more interesting charts. In the meantime, lots of practice for the homework.
From Ethan:
Returned the exam. Grades ranged from 40-something to 95. I suggested that the admirably large number of people with scores in the 90’s and high 80’s should make sure to challenge themselves. If they see a homework problem they know is easy (for them) they should find a harder one and do that instead. Just coasting might still get them an easy A, but would be a waste of their time and tuition since they wouldn’t be learning as much as they could. (I have made this kind of offer before. No one ever takes me up on it. Too bad.)
Started Excel, with the Wing Aero salary distribution. Worked through the first five(!) sections of Chapter 3, so touched on the three reasons for using a spreadsheet: Excel
- does large tedious calculations rapidly and correctly
- answers “what-if?” questions
- draws charts
The half the class with previous Excel experience helped the newcomers.
I talked about generic software package skills as well as Excel particulars:
- Applications often try to guess what you intend to do. That can be good or bad.
- To figure out something new, you can use Excel help, try google, or just play around (that’s my personal preferred strategy).
- Learn about undo. Save your work often.
- Some things work the same way in different applications (browsers, Word, Excel) – selecting with the mouse, cut and paste.
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