Describe the myogenic stimulation of the heart and how the regular contraction of the atria and ventricles is coordinated.

Do not include the autonomic nervous system in your answer.

Atrial fibrillation (AF) is a condition that causes an irregular heart rate. Scientists used a statistical test to investigate the association between different factors and the risk of developing AF.

Table 2 shows some of the scientists' results, including the probability (P) values obtained using the statistical test.

What can you conclude from Table 2?