A pharmaceutical company is testing the effectiveness of its vaccine across two different age brackets. They take a sample and split the participants up into two separate groups.Group Aconsists of 44 people who are between ages 13 and 18.Group Bconsists of 58 people between ages 19 and 26. After being administered the vaccine, it was found that 37 people from group A were immune to the virus and 42 people from group B were immune.

1. Why do we use the 'pooled proportion' instead of the null hypothesis in the denominator of the test statistic?
2. At a 10% significance level, is there reason to believe there is a difference in vaccine efficacy between Group A and Group B?