The gene ACTN3 encodes a protein that functions in fast-twitch mucles. People ca

Question

The gene ACTN3 encodes a protein that functions in fast-twitch mucles. People can be dlassified according to which genotype of this gene they have, RR, RX, or XX, and also according to which genetic allele they have, R or X. The study1 described here, examines the association between this gene and different subgroups of the population. All participants in the study live in Australia. The earlier exercises only induded the control group. Testing Genotypes for Fast-Twitch Muscles The study on genetics and fast-twitch musdes indudes a sample of elite sprinters, a sample of elite endurance athletes, and a control group of non-athletes. Is there an association between genotype classification (RR, RX, or Xx) and group (sprinter, endurance, control group)? Computer output is shown for this chi-square test. In each cell, the top number is the observed count, the middle number is the expected count, and the bottom number is the contribution to the chi-square statistic. RX XX Total Control 130 226 80 436 143.76 214.15 78.09 0.655 0.047 1.316 Sprint 48 107 53 35.28 8.901 6 52.56 19.16 0.395 9.043 Endurance 194 60 63.96 0.246 46 95.29 34.75 0.558 3.645 Total 243 362 132 737 Chi-Sq = 24.805, DF = 4, P-Value = 0.000 (a) What is the expected count for sprinters with the RXgenotype? For this cell, what is the contribution to the chi-square statistic? Round your answer for the expected count to two decimal places, and your answer for the contribution to the chi-square statistic to three decimal places. Contribution to the chi-square stati (b) What are the degrees of freedom for the test? df (c) what is the chi-square test statistic? What is the p value? What is the condusion of the test? chi-square s p-value Does the test indicate an association between these two variables? (d) For the cell which contributes the most to the chi-square statistic, is the observed count greater than or less than the expected count? (e) Which genotype is most over-represented in sprinters? Which genotype is most overrepresented in endurance athletes? LYang, N., et al, "ACTN3 genotype is associated with human elite athletic performance," American Journal of Human Genetics, 2003; 73: 627-631.

Explanation / Answer

a) expected count =52.56

chi square contribution =0.395

b) df =4

c) chi square test statistic =24.805

p value =0.000

conclusion : reject Ho

does this indicate association ---- Yes

d)

less then the expected count (sprint XX)

e)

RR is most over-represented

XX is most over-represented

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.