1. Nitrites are often added to meat products as preservatives. In a study of the effect of these chemicals on bacteria, the rate of uptake of a radio-labeled amino acid was measured for a number of cultures of bacteria, some growing in a medium to which nitrites had been added.
Here are the summary statistics from this study.
Group n x s
Nitrite 30 7880 1115
Control 30 8112 1250
Carry out a test of the research hypothesis that nitrites decrease amino acid uptake at the 2% significance level.
2. Two methods were used to teach a high school algebra course. A sample of 75 scores was selected for method 1, and a sample of 60 scores was selected for method 2. The results are:
Method 1 Method 2
Sample mean 85 83
Sample s.d. 3 2
Test whether method 1 was more successful than method 2 at the 1% level.
3. A private and a public university are located in the same city. For the private university, 1046 alumni were surveyed and 653 said that they attended at least one class reunion. For the public university, 791 out of 1327 sampled alumni claimed they have attended at least one class reunion. Is the difference in the sample proportions statistically significant at the 1% level?
4. Data taken from a random sample of 60 students chosen from the student population of a large urban high school indicated that 36 of them planned to pursue post-secondary education. An independent random sample of 50 students taken at a neighboring large suburban high school resulted in data that indicated that 31 of those students planned to pursue post-secondary education. Do these data provide sufficient evidence at the 5% level to reject the hypothesis that these population proportions are equal?