• Download a spreadsheet that simulates breeding 60 fruit flies
• The spreadsheet simulates the results of breeding fruit flies (F2 Generation – Second Filial?) where the expected outcome is a simple 1:3 Mendelian ratio of vestigial winged flies to winged flies
• The screen shot above shows an anomalous result – a chi-squared statistic well above 3.84, the critical value of the chi-square statistic at the 5% probability level with one degree of freedom
• I guess you should expect such an anomaly around 1 in 20 times – just press F9 for another breeding experiment
• The other tab of the spreadsheet calculates the data (I have left out the Yates’ correction usually used with 2 X 1 tables)

You can simulate the breeding experiment using two different coins (1p and a 10p say) – suppose HH is vestigial and HT, TH and TT are all winged, so that H is recessive allele and T is the dominant allele. This simulation can take a few minutes with a class of 15 or so as each person tosses their pair of coint 4 times.