A/B testing is a testing method that businesses use to test different designs and formats of a web page to determine whether a new web page is more effective than a current web page. Web designers tested a new call to action button on its web page. Every visitor to the web page was randomly shown either the original call to action button (the control) or the new call to action button. The metric used to measure success was the download rate: the number of people who downloaded the file divided by the number of people who saw that particular call to action button. The experiment yielded the following results:

a. What is the proportion (download rate) of visitors who saw the original call to action button and downloaded the file?

b. What is the proportion (download rate) of visitors who saw the new call to action button and downloaded the file?

c. At the 0.05 level of significance, is there evidence that the new call to action button is more effective than the original?

Variations Downloads Visiters Original call to action button New call to action button 351 485 3,642 3,556