Tuesday, January 12, 2016

Day 80: 6.1.2 Transformations & Intro to "r" (Correlation Coefficient)

Today's estimation was how many names on one section of the Vietnam War Memorial (to see these click on My Estimations at the top of this page). The last three classes noticed the dots on the left hand side of the section every 10 rows. So, they saw about 70 rows and estimated about 5 names per row. This got really close to the actual answer.

Only one student all day had an estimate that was way too high. Most students estimated between 200 and 800 names.
Students discussed in their groups how to setup their coordinate planes. Most agreed on 6 units in each direction. I encountered some students skipping a square near the origin when setting up their graph. I tried to catch as many with questions before they got too far into the activity.

A few students graphed (-5,0) at (0,-5). The biggest common mistake in translating 4 to the right and 2 up, was taking the right hand vertex of the triangle and moving it, and counting that as the bottom left hand corner vertex and drawing the rest of the triangle in the wrong place.

Some students reflected right underneath the triangle, instead of ACROSS the x-axis.

Some students were more successful at visualizing how the triangle rotated 90 degrees counter clockwise about point (3,-2). I asked them what they think "about (3,-2)" meant. Some dismissed it. Some thought that might be the center of the rotation. Others than thought that was the point that didn't stay the same. I liked how Gabby O described the rotation here:

In the last 15 minutes I had a volunteer who hadn't labeled their coordinates come under the document camera and label their coordinates so they could see what happened to the coordinates after translating (adding 4 to the x coordinate to move right, adding 2 to the y coordinate to move up 2 units). Then they observed what happened to the coordinates after reflecting across the x-axis (y coordinates became the opposite, and the x coordinates stayed the same.)

In accelerated, students made 4 first quadrant graphs and placed 3 points on there. In partners, they plotted the coordinates using Desmos and then making an LSRL by typing y1~mx1+b. They then wrote down the r value. They explored to figure out what the r value did. I had a great time talking to partnerships on a 1 on 1 basis, experimenting with changing one coordinate. We closed class with the following learning log, which was a summary of our class discussion. It answers the discussion questions in 6.2.1 Correlation Coefficient. They had previously matched 4 different r values to 4 different scatterplots with LSRL's on them.

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