The volleyball coach at a large high school wants to estimate the number of times players spike the ball during anygiven 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?
O using a sample of size 15
O using a sample of size 25
O constructing a 90% confidence interval
O constructing a 99% confidence interval
constructing a 90% confidence interval
at a 95% confidence interval By use of the table we have a critical value of 1.96, and so the margin of error is 1.96/(2 √ 900 = 0.03267, or about 3.3%.
A 90% confidence interval has a z-score (a critical value) of 1.645. In conclusion, the margin of error is 2.52%.
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