According to the data I found for the current first year students on the WPI website , the acceptance rate for WPI CS majors was 37%. The University wide acceptance rate was 42%. Most any other source would be dated. Be sure to enter CS in the “intended major” window. See https://public.tableau.com/profile/wpi.institutional.research#!/vizhome/IR_DataDashboard-AdmissionsDecisions/AdmissionsFunnel.
Went hunting on UMass, Amherst site to see what I could learn. It is interesting that the average entering student GPA for both Universities is tied at a respectable 3.89 across all majors. Access UMASS CDS @ https://www.umass.edu/search/#stq=CDS+2017-2018&stp=1
Because I was interested in face to face contact with faculty, I looked in section I ( Instructional Faculty and Class Size) of the common data sets for both universities At UMASS the ratio is 18 to one, at WPI the ratio is 13.1 to one and at Tufts University the ratio is 9 to one. That is a fairly big difference which reflects on my earlier discussion regarding strong access to well informed faculty in the the context of exploration of the STEM fields. It is an economic reality that access does drive up cost. I would argue that most larger Universities do not enjoy the same level of access and dialogue for undergraduate students. The MITs and Stanfords of the world have remarkable endowments which helps accomplish great ratios. To me, that is more important than the nefarious rankings.
It is also true that the cost of UMASS is lower. A point not to be ignored, but there are no free lunches!