A study was carried out to compare the effectiveness of the two vaccines A and B. The study reported that of the 900 adults who were randomly assigned vaccine A, 18 got the virus. Of the 600 adults who were randomly assigned vaccine B, 30 got the virus (round to two decimal places as needed).

Construct a 95% confidence interval for comparing the two vaccines (define vaccine A as population 1 and vaccine B as population 2

Suppose the two vaccines A and B were claimed to have the same effectiveness in preventing infection from the virus. A researcher wants to find out if there is a significant difference in the proportions of adults who got the virus after vaccinated using a significance level of 0.05.

What is the test statistic?