On a coordinate plane, a parabola opens down. It goes through (negative 2, negative 2), has a vertex at (1.5, 10), and goes through (5, negative 2). Over which interval is the graph of f(x) = –x2 + 3x + 8 increasing?

The first-serve percentage of a tennis player in a match is normally distributed with a standard deviation of 4.3%. if a sample of 15 random matches of the player is taken, the mean first-serve percentage is found to be 26.4%. what is the margin of error of the sample mean? a. 0.086% b. 0.533% c. 1.11% d. 2.22%