How do formative and summative assessments differ? 

Formative assessments are for the student. It's data that helps to identify what they know and what they need to practice. Summative assessments however, provide information to teachers, administrators and parents, about how much a student has learned as of a particular point in time.

In this video Marie distinguishes between formative assessment and formative instruction. Formative assessments primarily provide learners with feedback on progress, while formative instruction is used by teachers to collect evidence to guide learning.

Based on the work of Rick Stiggins, the 3 part formative assessment includes the teachers descriptive feedback, the students learning plan and possible learning strategies. 

When considering assessments, choosing between those which are common versus comparable depends on how the assessment is going to be used. Common assessments might be consistent across grade-levels, schools buildings or districts and have strict alignment to a particular set of standards. Comparable assessments however are more flexible classroom to classroom, and can have varying questions, formats and methods, while remaining true to the target.