DP Biology (first assessment 2025)

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Question 19N.2.HL.TZ0.c

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Date November 2019 Marks available [Maximum mark: 2] Reference code 19N.2.HL.TZ0.c
Level HL Paper 2 Time zone TZ0
Command term Deduce Question number c Adapted from N/A
c.
[Maximum mark: 2]
19N.2.HL.TZ0.c

The chi-squared value was calculated as shown. Deduce, with reasons, whether the observed ratio differed significantly from the expected Mendelian ratio.

[2]

Markscheme

a. yes/observed ratio did differ significantly «from the expected Mendelian ratio»
OR
expected ratio is 1:1:1:1 / 575 of each type / 25 % of each type ✔ Correct ratio not needed in first alternative of mpa

b. 3 degrees of freedom ✔

c. critical value is 7.815 «at the 5 % level / 11.345 «at the 1 % level» ✔ Accept mpc if candidates indicate the critical value of chi squared by circling it.

d. chi-squared value «of 1002.6» exceeds the critical value ✔

Allow other levels of significance as long as the critical value is correctly stated for the chosen level.

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