The Life of a Bar of Soap - The Results

(Posted 3/6/07)

So, what did I learn from all of this?

I moved all my data from the paper sheet that had been in my bathroom for a month. I put it all in this fancy new thing called a "spreadsheet".

Then, this fancy spreadsheet program I have can make a chart for me. It's amazing what these computers will do nowadays.

So, what does all of this tell us? Mostly that soap usage seems to be nearly perfectly linear. I was hoping to find some sort or curve that would show that you use more soap on a big bar, or on a little sliver. But, no. Really, this was such a boring result that it was hardly worth turning into a webpage. Hmm. Guess I'd better go think up something more worthy of my time.

My sister, Joyce, actually used my data for her math class (she's a teacher). Here's what she wrote:

Linear Regression for Kirk’s Soap Data

All values are rounded to six decimal places for the simple reason that six is my favorite number. A TI-83 Plus was used for all analyses.

 

Linear regression for y = start weight in ounces, x = shower number
y ≈ – 0.152857x + 4.279803
r 2 ≈ 0.995607
r ≈ – 0.997801

 

Linear regression for y = end weight, x = shower number
y ≈ – 0.152438x + 4.136576
r 2 ≈ 0.993829
r ≈ – 0.996909

 

Linear regression for y = end weight, x = shower number using only data for showers 2, 5, 8, 12, 18, 22, 28 (The data used for my Extended Algebra 1 Term 3 Review Packet.)
y ≈ – 0.145672x + 4.169839
r 2 ≈ 0.964286
r ≈ – 0.981981

I have a particular fondness for the last correlation coefficient.

 

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