It has been a weak month for blogging. I suppose this is still serving its purpose in letting me know to either learn more, or reflect more on what I am learning.
One tip I can give algbebra teachers is that if you want some linear data with which to give students that is not messy- not approximately linear- you can pull data from a life insurance company. Look at a product like 20-year, level-term life. Ask for data in intervals of $50,000 or $100,000 in insurance. The data is usually linear and it has a non-zero vertical intercept. You can compare different ages, or compare smokers and non-smokers to change the slope. Often the vertical-intercept will remain the same.