Final answer:
Not rejecting the null hypothesis in a chi-squared test for a dihybrid cross means the observed genetic ratios are consistent with expected Mendelian inheritance, such as a parent being heterozygous when a 1:1 ratio of traits is observed in offspring.
Step-by-step explanation:
Not rejecting the null hypothesis in a chi-squared test calculated in a dihybrid cross suggests that the observed genetic ratios of offspring are consistent with the expected ratios based on the Mendelian principles of inheritance.
For instance, in a test cross leading to a dihybrid ratio, if we do not reject the null hypothesis, it indicates that there is no significant difference between observed and expected ratios, thus suggesting that the inheritance of traits follows the expected Mendelian pattern of a dihybrid cross.
In context, if we perform a chi-squared test on a dihybrid cross and the null hypothesis is not rejected, it could be interpreted that, for example, a parent plant producing a 1:1 ratio of yellow to green offspring is indeed heterozygous for the trait being studied.
The conclusion we may draw from a test such as this is that the predicted genetic model aligns with the actual observations, within the probability limits set by the significance level of the test (e.g., a 5 percent level of significance).