A teacher looks at a graph in October. The last two scores are below the line. Is it time to change the plan? Maybe. Maybe not. Two points are not four, and the answer should not depend on who is reading the graph that week.
A decision rule is a statement written before the data come in: when the data look like this, we do that. This guide shows NCII's three rules, a worked example, and what to check before acting.
Why write the rule first
A rule removes mood from the decision. Without one, one team member sees a "bad week" and another sees a trend. NCII's handout offers three options and notes that they are not the only ones. The point is to pick one, write it in your progress monitoring plan, and use it the same way for every student.
NCII's three rules
| Rule | Minimum before you use it | Above the goal line | Below the goal line | Mixed or equal |
|---|---|---|---|---|
| Four-point analysis | 3 weeks of instruction and 6 data points; look at the 4 most recent | Increase the goal | Consider adapting the intervention | Keep collecting data |
| Trend line analysis | 4 weeks and 8 data points | Trend steeper: increase the goal | Trend flatter: consider adapting and assess fidelity | Same: keep monitoring |
| Median of last three | 4 weeks and 8 data points | Median above: increase the goal | Median below: consider adapting and assess fidelity | Right on the line: keep monitoring |
The handout also gives each rule's strengths and cautions. Four-point is simple and easy to see on a graph, but it needs consecutive points on one side of the line, and outliers in the last four can mislead. The trend line is highly accurate with enough data but needs calculation. The median of the last three limits the influence of outliers and allows timely adjustment, but may miss a trend if scores vary widely.
A worked example
A student has a baseline of 42, a goal of 70, and 12 weeks, so the aimline rises about 2.33 per week. After eight weeks the scores and aimline values are:
| Week | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
|---|---|---|---|---|---|---|---|---|
| Aimline | 44.3 | 46.7 | 49.0 | 51.3 | 53.7 | 56.0 | 58.3 | 60.7 |
| Score | 45 | 44 | 49 | 52 | 52 | 51 | 55 | 54 |
The minimums are met: more than three weeks and eight points. Under four-point analysis, look at weeks 5 to 8. Scores of 52, 51, 55, and 54 sit below the aimline values of 53.7, 56.0, 58.3, and 60.7. All four are below, so the rule says to consider adapting the intervention.
Under the median rule, the median of the last three scores (51, 55, 54) is 54, and the aimline in those weeks runs from 56 to 61. The median is below. Same conclusion. For the trend line, use the aimline and trendline calculator: a flatter trend points the same way.
The word is "consider." The rule does not say what to change. It says it is time to talk.
Check these before you change anything
NCII's handout tells you to assess fidelity when a trend or median is below the line. Fidelity means the intervention was carried out as planned. Before changing the plan, ask:
- Was the intervention delivered as often and as long as the plan says?
- Was the measure given the same way each week?
- Did anything outside school change, such as absences or a new class schedule?
- Is the aimline still right, or was the goal set too high?
If the answer to one of the first three is no, fix that and keep collecting. The goal-not-progressing checklist goes through these in order.
What adapting can look like
NCII describes data-based individualization as a process, not a program. Its flowchart runs from a validated intervention program to progress monitoring, then diagnostic assessment (or a functional behavior assessment for behavior), then intervention adaptation, then progress monitoring again. A student who responds stays on monitoring. A student who does not goes back to diagnostic assessment.
So the first thing to do with a "below the line" result is to find out why, not to try something at random. For behavior goals, NCII's guide lists three things to consider when progress is inadequate: review the data to adapt or intensify the intervention, change the reinforcer or increase the schedule of reinforcement, and revisit the ABC data to make sure the intervention addresses the correct function. Whatever you choose, write the change on the graph with a date, so the next weeks of data are read as a new phase.
When the data are above the line
All four points above the line, or a steeper trend, means the handout says to increase the goal. NCII's behavior guide offers two options when a student consistently meets a behavior goal at the first review: gradually increase the goal, or gradually fade supports while continuing to collect data. See goal mastered: now what.
When the points are mixed
Mixed points mean keep collecting. The MTSS Center's article describes the same idea: after six to nine data points, review the most recent four, and when they are mixed, do not decide yet. Use a schedule, such as every two weeks, so waiting has an end date.
Writing your rule down
Tell the family the rule
Parents see the graph too. Say the rule in plain words at the meeting: "If four scores in a row fall below the line, we will look at how the lessons are going and bring changes to you." A rule that everyone has heard in advance is easier to follow, and easier to defend, than one that appears after the data turn.
Common slips
- Deciding on two points. Wait for the minimum.
- Switching rules to get the answer you want. Pick one and keep it.
- Skipping the fidelity check. A flat line may reflect missed sessions.
- One person deciding alone. Share the graph with the team.
What these rules do not cover
The handout notes these are common options. Your state, district, or progress monitoring tool may use different thresholds, so follow local guidance. For how many points are enough in general, see how many data points before deciding. Terms are in the glossary.