1. A maintenance engineer has been approached by a supplier who promises less downtime for machines using its new molybdenum-based super lubricant. Of 120 machines maintained with the new lubricant, only 20% were out of service for more than an hour during the month of the test, while 30% of the 100 machines using the previous lubricant were down for more than an hour. Using the 0.05 level in an appropriate test, evaluate the supplier's contention. Using the appropriate statistical table, what is the approximate p-value for this test?
2. According to the National Center for Education Statistics, 88% of elementary, middle-school, and secondary- school students from families earning $75,000 or more per year use a computer at school, compared to 81% from families earning less than $20,000. Using a one-tail test at the 0.01 level, and assuming that the percentages are from independent samples of 500 families each, is the percentage of more-affluent students using computers at school signifi- cantly greater than for those from lower-income families?
Determine and interpret the p-value for the test. Source: Bureau of the Census, Statistical Abstract of the United States 2009, p. 163.