BRAINCAKEChi-Squared Test - Monohybrid Crosses
For a monohybrid cross there are normally two phenotype categories, so there is 2 − 1 = 1 degree of freedom, and the critical value at p = 0.05 is 3.84.
Worked example: pea plants heterozygous for height (Tt) are crossed. The offspring are 160 tall and 40 short, a total of 200. Is this consistent with a 3 : 1 ratio?
Null hypothesis: there is no significant difference between the observed numbers and the numbers expected from a 3 : 1 ratio.
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Key terms in this lesson
- degrees of freedom
- The number of categories in a statistical test minus one.
- critical value
- The value of a test statistic, such as chi-squared, that must be reached or exceeded for a difference to be significant.
- null hypothesis
- A statement that there is no significant difference between observed and expected results, and any difference is due to chance.
More in Genetic Information
- Dihybrid Crosses
- Drosophila
- Probability
- Chi-Squared Test
- Chi-Squared Test- Dihybrid Crosses
- Gene Linkage
- Identifying Linked Genes
- Chromosome Mapping
All 30 lessons in Genetic Information · All Edexcel A-level Biology topics