1. You would like to start an ISP and need to estimate the average Internet usage of households in one week for your business plan and model. How many households must you randomly select to be 95 percent sure that the sample mean is within 1 minute of the population mean m. Assume that a previous survey of household usage has shown s = 6.95 minutes.

2. A survey estimated that 20% of all Americans aged 16 to 20 drove under the influence of drugs or alcohol. A similar survey is planned for the Philippines. They want a 95% confidence interval to have a margin of error of 0.04. a. Find the necessary sample size if they expect to find results similar to those in the United States. b. Suppose instead they used the conservative formula based on ?= 0.5. What is now the required sample size?

3. The National Centre for Mental Health published an article stating that in any one-year period, approximately 9.5 percent of Filipino adults suffer from depression or a depressive illness. Suppose that in a survey of 100 people in a certain town, seven of them suffered from depression or a depressive illness. Conduct a hypothesis test to determine if the true proportion of people in that town suffering from depression or a depressive illness is lower than the percent in the general adult Philippine population.

4. Your statistics instructor claims that 60 percent of the students who take his Elementary Statistics class go through life feeling more enriched. For some reason that he can't quite figure out, most people don't believe him. You decide to check this out on your own. You randomly survey 64 of his past Elementary Statistics students and find that 34 feel more enriched as a result of his class. Now, what do you think?

5. Researchers interviewed street prostitutes in urban and rural areas. The mean age of the 100 urban prostitutes upon entering prostitution was 18 with a standard deviation of six. The mean age of the 130 rural prostitutes upon entering prostitution was 20 with a standard deviation of eight. Is the mean age of entering prostitution in the urban areas lower than the mean age in the rural areas? Test at a 1% significance level.

6. A study was conducted to investigate the effectiveness of hypnotism in reducing anxiety levels. Results for randomly selected subjects are shown in the table below. A lower score indicates lower anxiety level. The "before" value is matched to an "after" value and the differences are calculated. The differences have a normal distribution. Are the anxiety level measurements, on average, lower after hypnotism? Test at a 5% significance level. Subject A B C D E F G H Before 6.6 6.5 9.0 10.3 11.3 8.1 6.3 11.6 After 6.8 2.4 7.4 8.5 8.1 6.1 3.4 2.0

7. The table below shows the scores on final exams from several randomly selected classes that used the different delivery types. Assuming that all distributions are normal, the population standard deviations are approximately the same, and the data were collected independently and randomly, are the means for the final exams the same for all statistics class delivery types? Use a level of significance of 0.05. Online 72 84 77 80 81 HYBRID 83 73 84 81 FACE-TO-FACE 80 78 84 81 86 79 82

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