Analyzing Student Datat in a Spreadsheet

The data indicates that all students have improved their test scores or increased their knowledge of the content.  The student growth line of Kathrine is very interesting.  She started out with the lowest test score of 120 and then shot up to 180.  She then dropped back down to a test score of 160 and then back up to 180.  Most students consistently increased their test scores.  Kathrine's score seems to fluctuate.  What is causing the fluctuations in her growth chart?

I had some trouble hiding data, so I followed Barry's advice and copy/paste the data on a seperate sheet so I could create a chart with the scores lower than 192.  I think the Excel program is ok.  I don't have alot of experience with Excel but I do think the Excel program on Google Docs creates a bit of busy work.  We should be able to hide data so a chart can be created with the data we have showing.  Also, I'm not sure about the publishing section.  I posted my chart earlier today and when I later went to edit the post, my chart was gone.   It could be my computer because it has had problems functioning in Google Docs today.