Here is an interesting study completed within the City University of New York system on co-requisite remediation. They compared three groups using a randomized trial - Elementary Algebra students, Elementary Algebra with Supplemental Instruction, Elementary Statistics with Supplemental Instruction.  The 721 participants were randomly assigned to one of those three groups.  Guess what?  The pass rates for the courses were as follows:

• Elementary Algebra:  39%
• Elementary Algebra with SI: 45%
• Statistics with SI: 56%

Read about the study here.

The Sullivan Statistics series offers an Introductory Statistics text with Integrated Review.  The Integrated Review content is based on Sullivan's popular Developmental Mathematics series.