1. The Major League Baseball (MLB) sets manufacturing standards for baseballs. For example, the weight of the baseball needs to be on average 145 grams. In other words, if it is different than 145 grams, MLB will reject the set of baseballs. Suppose a manufacturer introduces a new kind of baseball and provides a randomly selected sample of them for testing. Based on the mean weight in the sample, the MLB comes up with a P-value of 0.25. Explain in this context what the 25% represents.

2. Peoples magazine conducts surveys to gauge how the Internet and technology impact daily life of people. One might suspect that younger and older respondents might differ in their opinions of whether computers and technology give them more control over their lives. A subset of the data from this survey shows the mean ages of two groups of respondents, those who reported that they believed that computers and technology give them more control and those that reported less control. Give the StatCrunch output to support your answer.

a) Find the 90% confidence interval for the difference in mean age between the two groups of respondents.

b) With this confidence interval, can you say the two groups are different? Explain.

Group	n	mean	stdev
More	72	49.3	20.1
Less	28	49.0	18.2

3.

A marketing company is trying to decide between IT training conducted in-house and the use of third party consultants. To get some preliminary cost data, each type of training was implemented at two of the firm's offices located in different cities. The table below shows the average annual training cost per employee at each location. Are the mean costs significantly different? Assume that the assumptions for inference are satisfied.

a) Write the appropriate hypotheses.

b) Use computer output provided for this hypothesis test. Explain what the P-value means in this context. Let = 0.05

c) State a conclusion about IT training costs.

IT Training n Mean SD

In-House 270 $690.00 $35.00

Consultants 230 $702.00 $51.00

Two sample T summary hypothesis test:

H_A : ₁ - ₂ 0 Hypothesis test results:

Difference	Sample Diff.	Std. Err.	DF	T-Stat	P-value
1 - 2	-12	3.981	395.426	-3.015	0.0027