Question 1 in the Massachusetts Leagues' study of the Ballot Question Process asks "Should additional efforts be made to ensure petition summaries are written for the greatest understanding by voters?"
Petition summaries are printed on the petitions used to gather signatures. If the measure makes it onto the ballot, then these 150-word summaries are printed on the ballot and in the red "Information for Voters" booklet that voters get in the mail. A majority of voters read these summaries.
In a study done by political scientists of ballot questions asked between 1997 and 2007, Massachusetts' summaries were scored at the equivalent of 14 years of education on average, using a popular standardized tool for indicating the readability of a passage in English. One of the 2018 ballot questions (the one dealing with campaign finance and corporate personhood) required 19 years, the equivalent of more than a Masters degree.
Oklahoma is the only state with a readability requirement written into law. It is also the only state to achieve an average rating of about grade 8, that is, easily comprehensible by 13-15 year olds.
Ballot measure readability scores for 2018 can be found on Ballotpedia.org.
In defense of simple reading scores: Rudolf Flesch: How to Write Plain English.
Question 1 is on page 2 of the Study Guide.