Question 2: For a study of free-living populations of the fruitfly Drosophila su

Question

Question 2: For a study of free-living populations of the fruitfly Drosophila subobscura researchers placed baited traps in two woodland sites and one open-ground area. The numbers of male and female flies trapped in a single day are given in the table below: ~ Woodland Site I 89- 31 120 Woodland Site IIOpen Ground* Males Females^ Total- 34 20 54H 74p 1361 210 a) Does this table suggest that there are differences between the three different sites in the sex ratio using a global chi-square hypothesis test? b) If there are differences, which sites appear to be different from each other? (Be sure to use a Bonferroni correction)-+'

Explanation / Answer

a)

here TS = 49.74 > critical value = 5.99

hence we reject the null and conclude that there are difference between the three different sites

c1 c2 c3 sum r1 89 34 74 197 r2 31 20 136 187 sum 120 54 210 384 Eij 1 2 3 expected 1 61.5625 27.70313 107.7344 2 58.4375 26.29688 102.2656 0i 89 34 74 31 20 136 Ei 61.5625 27.70313 107.7344 58.4375 26.29688 102.265625 sum (Oi-Ei)^2/Ei 12.22849 1.431269 10.56309 12.88242 1.507808 11.12796266 49.74104 critical value 5.991465

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