Sunday, January 24, 2010

Lines Project

In algebra 1 we've covered most line topics I think are important:
* calculating slope from a graph and from 2 points without a graph
* looking at a graph and finding the line equation in all 3 ways (standard, pt-slope,slope-int)
* being given either 2 points or a point and a slope and calculating any of the 3 equations.
* looking at any of the 3 line equations and graphing
* looking at any of the 3 line equations and finding 5 points on the line (and the intercepts)
* seeing that if you have a graph and it's line equation in any form, that you can plug in any point on the line and it will "work" and plug in any equation not on the line, and it won't work in the equation.
(I've probably missed some, but this is what I remember)

We still have to talk about parallel and perpendicular lines, but soon we'll move on to systems of equations. Before we do that, I thought that this would be the perfect time to assign a line project to my students. In all their later topics and math courses, lines will just be an aside where it's already assumed they have learned about them.

We had a discussion about positive and negative linear correlation and no correlation and correlation that is not linear. We went through the process of creating best fit lines and using that line to make a prediction for another point that is not represented by your data. Then I discussed that in real life, people collect data, and if they all fell on a straight line, the mathematicians/scientists would faint from the rareness of this occurrence, and that usually, if the data seems to be linear, it'll look like our scatter plots that have a linear correlation, and THAT'S how this is used in real life. People make a model and then use that model to make predictions.

Then I assigned this project that I will collect in a succession of 3 class periods. I already have had one student send me her data that was interesting. She found information about teacher pay from the 40's to the 2000's, and you can see that it looks linear until about 1980, and then there's a BIG leap of the points and then it looks linear again. After a back and forth e-mail discussion, she found that some site stated that there was a 400% increase in pay in 1980 .... hmmm, haven't verified that, but I remember some of my older teacher friends mentioning their super low pay in the 70's.


  1. Love the project idea.

    I just opened a box account. Not sure how to use it yet. I'll try to play around with it later and post my linear art project.

  2. Nice! Thanks for posting it. I'm saving it for the fall.

  3. Thank you .... I'm looking forward to what they come up with.

    Mrs. H: once you upload a file, when you click on "share" it shows you a link address that you can paste into your blog.

    Ms. Cookie

  4. Sarah4:58 PM

    I did a similar project, but had the students create graphs in Excel and use the line of best fit that Excel gave them.

  5. Hi Sarah,

    I thought about that, and my thinking was that then the line equation would somehow magically be created, and they may not think about how it was done. This way they do the dirty work and test it out and see where things come from.

    Ms. Cookie