Why are some saved and others not?

Today's program was spent discussing issues in Reformed Theology. I briefly addressed Steve from Triablogue's comments, and then went into a discussion from the program Christ the Center. The Reformed podcast Christ the Center had Dr. Lane Tipton of Westminster Seminary Philadephia to discuss an essay of B.B. Warfield titled the Plan of Salvation. In this discussion, Tipton made claims about Lutheranism that are inaccurate; he argued that Lutherans believe in conditional election to salvation based on non-resistance to God's grace. I spent the majority of the program demonstrating why this is not true and addressing the question "Why are some saved and others not?"