Final answer:
Use the Site Search report to find new keywords for advertising campaigns, as it reveals what visitors are searching for on your site. Other probability-related details seem out of context, as keyword research focuses on visitor interests rather than advertisement placements.
Step-by-step explanation:
When looking for new keyword ideas for your search advertising campaigns, Site Search reports can be very useful. The Site Search report shows you what terms are being searched for within your site. This information can indicate what your visitors are interested in and what they expect to find on your site. If you see certain search terms consistently appearing, these could potentially be valuable keywords to incorporate in your search advertising to draw more traffic.
Regarding the probability-related questions, they seem out of context for the task of finding keywords. Usually, keyword research does not involve advertising on individual pages but rather focuses on what potential customers are interested in by looking at their search behavior. Probabilities would be more relevant if you were trying to determine the likelihood of visitors encountering certain advertisements on different pages of a website, which is different from selecting keywords for search advertising campaigns.