Measuring effectiveness in ministry is a tricky process. It is all too easy to gauge our success by the number of people attending each Sunday or the feedback they offer us after a worship service. We look to see if people are singing, are they responding to the sermon, how many came down for the altar call, etc. While these can be significant indicators of what is happening at large, we must remember that these markers only judge outward appearances... they do not look at the heart. When we fail to recognize that profound things can occur in the heart without presenting themselves outwardly, or that an outward "worshipful appearance" can be masking a sense of hopelessness or confusion, we can easily confuse success and failure.
Louie Giglio spoke recently about a ministry opportunity that had unexpected results (approx. 4 minutes, edited for time):
What we don't see, or more specifically what we don't know, is what is going on between the heart of the individual and Jesus Christ. While it is our goal to help others know Jesus on a deeper level, ultimately the best thing we can do is show them what He means to us, what He has done in our lives. We can no more successfully force a relationship between a person and Jesus Christ than we can setup a successful arranged marriage. I believe our job is simple: follow and trust in the Holy Spirit. Do everything you can to show them Jesus, then trust God for the outcome. You may never see their love for Jesus blossom, but that does not mean you have failed. If you respond to God's directives and trust in the Holy Spirit, you have succeeded.
I do feel we can measure effectiveness in ministry, but more so by measuring ourselves. Look at what things occurred in a worship service (or your life) that "may have helped" or "may have detracted" from people experiencing God. Measure your actions, not others.
