Question 21N.1A.HL.TZ1.35
| Date | November 2021 | Marks available | [Maximum mark: 1] | Reference code | 21N.1A.HL.TZ1.35 |
| Level | HL | Paper | 1A | Time zone | TZ1 |
| Command term | Question number | 35 | Adapted from | N/A |
A dihybrid cross was carried out between two plants to determine whether the genes for seed shape and colour are linked. If the genes are unlinked, the expected ratio of 9:3:3:1 should occur. A chi-squared test was carried out on the observed results of the cross. The critical value for chi squared at the 5 % level of significance in this test was 7.82. The calculated value for chi squared was 6.25. What can be concluded from this data?
A. The results prove that the genes are linked.
B. The results prove that the genes are unlinked.
C. There is significant evidence that the genes are linked.
D. There is significant evidence that the genes are unlinked.
[1]
D
Although slightly less than half of candidates answered correctly and the discrimination index was respectable rather than good, this was a relatively successful question on statistical hypothesis testing, which is typically a difficult area both for question setters and candidates. Performance seems to be improving in this part of the program.
