Chi Square Analysis Practice Problems

The normal range of chi-square values is determined by the number of degrees of freedom (df) and the level of significance (alpha) employed. In general, a lower chi-square value implies a better match between the observed and predicted values, whereas a greater number suggests a worse fit. What does it mean when the chi-square value exceeds the critical value?

If the F2 generation yields 60 individuals with the dominant phenotype and 28 individuals with the recessive phenotype, with the predicted ratio being 9:3:4, what is the chi-square value for a dihybrid cross between two genes showing epistasis?

A sample of 100 people includes 40 people with the Bombay blood type and 60 people with the ABO blood type. What is the expected frequency of individuals with an ABO blood type?  

The observed and expected frequencies of blood types A, B, AB, and O in a sample of 500 people are given as follows:

The observed frequencies for blood groups A, B, AB, and O are 150, 100, 50, and 200, respectively.

The expected frequencies for blood groups A, B, AB, and O are 180, 140, 30, and 150, respectively. 

What is the chi-square value?

What is the degree of freedom in a chi-square analysis of a genetic cross with four phenotypic classes?

A dihybrid cross is made between two genes exhibiting epistasis; the F2 generation produces 68 individuals with the dominant phenotype and 28 individuals with the recessive phenotype. If the expected ratio is 9:3:4, what is the chi-square value for this set of data?

A chi-square test is used to examine a genetic cross with a total of 200 offspring. What may be concluded if the estimated chi-square value is 5.89 and the p-value is 0.015?

A genetic cross between two pea plants with yellow seeds (YY) and green seeds (yy) results in 100% F1 offspring with yellow seeds. What is the expected phenotypic ratio of the F2 generation produced as a result of a self-cross of F1?  

To determine whether there is a link between a gene and a disease, a researcher used a chi-square test. The obtained p-value was 0.03. What conclusions may be drawn from this outcome?

If the smooth and wrinkled-seeded peas have the same expected values of 35 and observed values of 27 and 22, respectively, which of the following gives the correct probability range?

If the calculated P-value is 0.003, what does it imply?

In conducting a chi-square test, which of the following is considered the null hypothesis?

What is the main purpose of the chi-square test?

A male mouse with black fur (Bb) was mated to a female mouse with white fur (bb). The female produces a litter of 12 pups with 7 black and 5 white fur. Determine the chi-square value for the fur color.

The trait for round seed (R) is dominant over wrinkled peas (r), and yellow pea color (Y) is dominant over green (y). A dihybrid cross between two heterozygous pea plants is performed (RrYy x RrYy). In a total progeny of 1200 peas, calculate the expected progeny of round yellow peas.

The trait for round seed (R) is dominant over wrinkled peas (r), and yellow pea color (Y) is dominant over green (y). A dihybrid cross between two heterozygous pea plants is performed (RrYy x RrYy). The following phenotypic frequencies are observed: 

800 round yellow peas; 241 round green peas; 220 wrinkled yellow peas; 66 wrinkled green peas. Based on the above results, the statistical value calculated by the chi-squared test is as follows:

The P value is the probability, for a certain statistical model, that the statistical summary would be either equal to or more extreme than the actually observed findings if the null hypothesis were to hold. If the p-value is _________, the null hypothesis is rejected.

In genetics, the _____ is used to show if alleles in a population are performing differently from what would be predicted.