mobile phone usage

I got my Cingular bill today, and I saw that I had about $16 in usage charges from going over my minutes. Ugh. Being on a shared plan, it's either my fault, or my mom's fault. Knowing my usage habits, I was pretty sure it was not me. After looking through the minutes used on the statement, I confirmed by suspicion.

But for the sake of fairness, and practicing Pivot Tables and Excel, I decided to dig a little deeper. Here's a summary of what I found. My mom seems to pay attention to when calls are being made. A lot of her calls are made after 9pm. On the other hand, it seems that the few calls made during the day tend to consume a lot of minutes. The other surprise is that I seem to make a ton of short calls around 6pm or so.