The volleyball coach at a large high school wants to estimate the number of times players spike the ball during any given game. She randomly selects 30 games and records the number of spikes. The coach constructs a 95% confidence interval for the true mean number of spikes players make in a game. Which of the following would decrease the margin of error? using a sample of size 15 using a sample of size 25 constructing a 90% confidence interval constructing a 99% confidence interval