Chapter 8, Problem 108H

Suppose that 14 children, who were learning to ride two-wheel bikes, were surveyed to determine how long they had to use training wheels. It was revealed that they used them an average of six months with a sample standard deviation of three months. Assume that the underlying population distribution is normal.

a. 1 i. $\bar{x}$ ______

ii. s_x=________ .

iii. n _______

iv. n - 1 _________

b. Define the random variable X In worth.

c. Define the random variable $\bar{X}$ in worth.

d. Which distribution should you use for this problem? Explain you choice.

e. Construct a 99°o confidence interval for the population mean length of time using training wheels.

i. State the confidence Interval.

ii. Sketch the graph.

iii. Calculate the error bound.

f. Why would the error bound change if the confidence level were lowered to 90%?