two questions about SCRUM learn materials
by preparing myself for certification exam, there are following 2 (inconsistencies/ questions) raised:
1) in Scrum guide (July 2013) page 6: the optimal size of dev. team is defined as (3 =< optimal size =< 9 )
but in the ScrumReferenceCard written by AuthorMichael James , the size is defined as :7 ± 2 members
this is slightly different ( 5 =< optimal size =< 9 ). what is now the lower limit for a optimal S. dev. size?
2) in the S. Guide (July 2013) page 12 , it defines timebox for the retrospective meeting (for a 4 weeks sprint): 3 hours.
"The Sprint Retrospective occurs after the Sprint Review and prior to the next Sprint Planning. This is a three-hour time-boxed meeting for one-month Sprints."
but in the book (Software in 30 days/ 2012) chap5 page 60 says that upper limit of such meeting is 4 hours?
"... this meeting should not never exceed four hours."
I probably will for the certification exam take the version which are written in the current scrum guide, but should the new versions handel these inconsistencies?
7 ± 2 members is also the range that is cited in the Scrum Primer, which broadly reflects the position of the Scrum Alliance. It's likely that the Scrum Reference card is reflecting this position also. For scrum.org exams you should go by the recommendations contained in the Scrum Guide.
As for a 4 hour Sprint Retrospective, I think that must be a typo in the book. Good spot.
If you want to take the PSM assessment, Scrum Guide is the reliable source.
For the purpose of the exam I would go with the Scrum Guide recommendation 3 to 9 and 3 hours. However, I am wondering if what is the actual used by your scrum teams for sprint retrospectives. I have seen 90mins to 2 hrs