1. The actual voltages of power packs labeled as 12 volts are as follows: 11.77, 11.90, 11.64, 11.84, 12.13, 11.99, 11.77. Referring to the above, a confidence interval for this sample would be based on the t distribution with __________ degrees of freedom.

2. A national trend predicts that women will account for half of all business travelers in the next three years. To attract these women business travelers, hotels are providing more amenities that women particularly like. A recent survey of American hotels found that 70% offer hairdryers in the bathrooms. Consider a random and independent sample of 20 hotels. Find the probability all of the hotels in the sample offered hairdryers in the bathrooms.

3. Records of an automobile insurance company show that 10% of its policyholders were involved in an accident during the past year. A random sample of 400 policyholders is to be selected. The probability that the sample proportion of policyholders involved in an accident is between 9 and 10% is: