It%20can%20be%20used%20to%20measure%20retention%2C%20loyalty%2C%20success%20of%20a%20marketing%20initiative%20and%20other%20metrics%2C%20very%20vital%20to%20monitor%20in%20case%20of%20a%20startup.%20Cohort%20analysis%20not%20only%20helps%20identify%20the%20exact%20pain%20point%20but%20also%20suggests%20how%20to%20rectify%20it.