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Overview

Dash360 Risk has three related but distinct features that people often blur together. Two of them are correlation (they link uncertainty so items move together), and one is mapping (it routes a risk’s schedule impact to activities). Keeping them separate is the key to reading your Monte Carlo results correctly.
Correlation links like to like: a risk to another risk, or an activity to another activity. There is no risk-to-activity correlation in Dash360. The only thing that links a risk to an activity is Activity Mapping, and that is routing, not correlation.

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What “correlation” means in Dash360

By default, every activity and every risk is sampled independently in each Monte Carlo iteration. Independent draws tend to cancel out: in a given iteration one item lands high while another lands low, so the totals average toward the middle. That understates the real spread of the total, because in the real world related items often move in the same direction at the same time. Correlation is how you tell the simulation that certain items move together. When you correlate items, they share their random draw in each iteration, so they tend to land high together or low together. Each correlation group has a single coefficient from -100% to +100%:
  • +100%: the members take the driver’s draw exactly (they fully move together).
  • A positive value below 100%: the members move partly with the driver and partly on their own.
  • 0%: independent (no effect).
  • A negative value: the members tend to move opposite the driver.
Correlation is applied at the random-draw level using a single-factor Gaussian copula, so the shape of each item’s own distribution is preserved. Positive correlation widens the total cost and finish-date distributions (higher P80 and P90) because related items no longer cancel each other out. That is the more realistic result. The graphs keep the same shape and chart types; only the numbers shift.
The point of correlation is honesty about spread, not a bigger mean. Correlation barely moves the average result; it widens the tails, which is exactly where contingency decisions (P80, P90) are made. For the underlying math, see How the Dash360 Monte Carlo Works.

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The three mechanisms

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1. Activity-to-Risk Mapping (routing)

Mapped Activities Where: the Activity Mapping area of the Add/Edit Risk form (Risk Register). What it is: it maps a risk to the specific schedule activities its schedule impact should hit. This is what lets the schedule Monte Carlo apply the risk’s delay to the right activities on the critical path. Why you do it: so a risk’s schedule impact lands where it actually occurs, and so the Activity Drivers analytics chart can show which activities carry the most risk exposure. A risk with no activity mapping still contributes, but its schedule impact is applied to the project finish directly instead of to specific activities. What it affects: where a risk’s schedule impact is applied. It uses a Mapping Mode:
  • Relative (default): distribute the impact across the mapped activities by each activity’s Weight (%).
  • Absolute: apply the full impact to each mapped activity.
What it does NOT do: it is not correlation. Mapping never changes whether or how strongly two risks (or two activities) move together. Availability: This feature is available in all versions.

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2. Risk-to-Risk Correlation (Pro)

Risk Correlation Where: the Correlation column on the Risk Register grid. What it is: pick a driver risk, then select the risks that are correlated to it. Correlated risks share their random draws, so they tend to occur in the same iterations, and when they do, their impacts tend to be large (or small) at the same time. All three of a risk’s draws are correlated: occurrence probability, cost impact, and schedule impact. Why you do it: when risks share a common cause (the same vendor, the same technology, the same site condition), treating them as independent understates your true exposure. Correlating them restores the realistic “they tend to hit together” behavior. What it affects: it widens the total cost and finish-date distributions. Because correlation acts on the shared draw before the impact is applied, it affects both the Risk (pre-mitigation) and Mitigated Risk (post-mitigation) result views, not just one of them. Availability: This feature is only available in the Pro version.

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3. Activity-to-Activity Correlation (Pro)

Activity Correlation Where: the Correlation column on the Cost & Schedule Uncertainty tree (Risk Analysis page). What it is: pick a driver activity, then select the activities that should follow it. Each iteration the follower activities inherit the driver’s uncertainty draw, so they run long or short together. Because an activity’s cost draw follows its schedule draw, correlated activities move together on both duration and cost. Why you do it: activities that share a driver (the same crew, weather window, or supplier) genuinely tend to run long or short together. Correlating them captures that shared behavior instead of letting it cancel out. What it affects: it widens the total cost and finish-date distributions. Availability: This feature is only available in the Pro version.

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How they relate

The clearest way to hold all three in your head:
  • Correlation changes how big and how together impacts are. It is always like-to-like (risk to risk, or activity to activity).
  • Mapping changes where a risk’s schedule impact lands (which activities absorb it).
They compose cleanly. A risk that correlation has made larger or more co-moving still lands on whatever activities its mapping specifies. Correlation decides the size and timing of the hit; mapping decides its destination on the schedule.
Activity Mapping and Risk-to-Risk correlation are independent. Editing a risk’s mapped activities does not change any correlation between that risk and another risk, and adding or removing a correlation does not change a risk’s activity mapping. Mapping only reroutes where a risk’s (possibly correlated) schedule impact is applied.

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Side-by-side comparison

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When to use each

  • Map a risk to activities whenever the risk has a schedule impact and you know which activities it delays. Without a mapping, the delay is applied to the project finish instead of to a specific activity, and the risk will not appear in the Activity Drivers chart.
  • Correlate risks when two or more risks share a common cause and would realistically hit together. Independent risks understate the P80 and P90 you need for contingency.
  • Correlate activities when two or more activities share a driver (crew, weather, vendor) and would realistically run long or short together.

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Frequently asked questions

No. Correlation is applied to each risk’s random draws before any impact is calculated, so it affects both result views: the Risk graph (pre-mitigation) and the Mitigated Risk graph (post-mitigation). You can also set correlations on risks whether or not they are mitigated.
No. These are two separate features. Risk-to-Risk correlation links one risk’s uncertainty to another risk’s uncertainty; it is always risk-to-risk. Activity Mapping links a single risk to the schedule activities its impact should land on; it is routing, not correlation. There is no risk-to-activity correlation in Dash360, so you cannot correlate a risk directly to an activity.
There is no dedicated per-activity view of correlation impact. Correlation’s effect shows up in the aggregate Monte Carlo output: wider tails and higher P80 and P90 on both cost and finish, plus shifts in the sensitivity or tornado view. The clearest way to see it is to run the simulation with correlation and again without it, then compare the percentiles.
No. Mapping and correlation are independent. Changing the mapped activities on a risk only changes where that risk’s schedule impact lands; it does not change any Risk-to-Risk correlation the risk participates in. Likewise, adding or removing a correlation does not change the risk’s mapping.
Not in this release. Each activity or risk can belong to only one correlation group, and an item cannot be both a driver and a follower at the same time.