When testing Marketo Measure, be sure to first clear cookies and use a unique email address for each test. The email address does not need to be real–it only needs to be a unique address that does not belong to any of your Salesforce records (e.g., email@example.com, firstname.lastname@example.org).
Cookies can be cleared in the settings section of your browser, select tools and clear browsing data. A test begins before the search and ends with a form submission. You can test through organic search or through a company advertisement. Make sure to clear cookies again before every new test you conduct.