Earlier in this chapter, when we discussed web ads and creating an explanation page for them, we covered the basic information that participants are looking for when they’re deciding if they will do our study – items including:

• What the study is for
  
  
• How long it will take
  
  
• What's in it for them
  
  

Because people are continually asked for their input, and also have to sift through spam emails, most have learned to sift these invitations ruthlessly. If we want their participation in your study, we must make our case clearly and concisely. This means that:

• The invitation should be from a person or organization they know (and preferably have a relationship with), as discussed in Using email lists earlier in this chapter.
  
  
• The basic pitch should be clear at a glance.
  If this is a web ad, the ad text needs to convey the basic proposition. If this is an email invitation, the subject line must perform this duty.
  
  
• The person’s most immediate questions must be answered by skimming the invitation.
  Not only do we need to answer basic questions (How long will this take? What do I get in return?), but we need to do it in a way that a busy, only slightly interested person will absorb.
  
  
• It should sound like something they're familar with, so call it a "survey".
  As we mentioned in Using web ads earlier in this chapter, the term "tree test" is unfamiliar, so we use the much more familiar "survey".
  
  
• There must be a clear way to start the study.
  This seems obvious, but we’ve seen lots of invitations that included so many other links (to more information, terms and conditions, privacy statements, etc.) that it took some effort to figure out which link was for the study itself.
  
  

Here’s an example of an effective email invitation. Over time we’ve refined it to maximize the response rate:

Note that the subject line offers a clear and concrete proposition, the “start study” link is early and prominent, the most important questions are listed first, and the whole message is formatted to be easy to skim.

Also note that this content is very similar to what we put in our web-ad explanation page – see Using web ads earlier in this chapter.

Next: Offering incentives