

August 19  August 26
Question of the Week 
Name: Jovana
Status: student
Grade: other
Location: NY
Country: Sweden
Date: Winter 20132014
Question
I am investigating the acceptance of 9:3:3:1 ratio in dihybrid cross (Mandels law of independent assortment).
I am using 4 different genotypes of corn cobs (kernels): yellow and smooth, yellow and wrinkled, purple and smooth, purple and wrinkled. What could be my control variables? I just have 1 which is the same method of counting. Also I dont know which type of uncertainties I need to calculate. I was thinking to say that while counting I made uncertainy of +4 kernels, so if i do 4 trials, I will have uncertainty of +16 kernels. What do you think about that, and what more could I do? 
Answers from Our Expert Staff 
You did not say what grade level you were at, so I'll give you the college level answer I would give a student.
Since you are comparing your data an expected ratio, you no not need a control. The theoretical value is your "control". You need to use the chi squared test of goodness of fit to see if your actual data matches the theoretical expected within the bounds of probability. That is, any differences between the theoretical distribution and your data is due to random chance. Any good elementary statistics book should help you do the math.
Need any more help, get hold of me directly.
Bob Avakian
Oklahoma State University Institute of Technology (OSUIT)

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