We do this by dividing 360°<span> by the number of sides, which is 8. (b) Calculate the size of each interior angle in the regular octagon. We do this by subtracting the size of each exterior angle, which is 45°, from </span>180°<span>. A regular polygon has equal exterior angles of 72°</span>
Let be the true (population) mean of statistics exam scores. We have a large random sample of n = 36 scores with a sample mean (sample mean score) of . We know that the population standard deviation is . A pivotal quantity is which is approximately normally distributed and where , and so, . Therefore the 90% confidence interval is (68-(1/2)(1.6449), 68+(1/2)(1.6449)), i.e., ( 67.18, 68.82)