activities that are elements of the subset
may be changed.
•;Action: An action is defined as a move
on the trade-offs of an activity that may
potentially change an activity’s cost
and associated duration. This need
not be the case, because many students check whether the action leads
to an immediate cost decrease or not.
If there is no improvement, it is possible that the activity’s cost and duration are reverted. Actions can go from
simple to more advanced operations.
An overview of the types of actions and
accompanying descriptions are presented in Table 3.
The rationale for the different refinement phases leads back to the nature
of the PSG, in which students only
have a limited amount of time to make
changes and advance to the next decision moment; therefore, it is necessary
to focus on the activities that are most
important. In order to clarify the building blocks of the solution strategies,
the stepwise selection and action will
be illustrated using a straightforward
Link to the Student Data
The previous section outlined the dif-
ferent building blocks of a solution
strategy. The aim of this section is to
connect the five components (focus,
activity criticality, ranking, intensity,
and action) to the student data listed in
priority rules are easy to apply and
in line with techniques that are used
to give priority to certain activities.
A tight match could be witnessed
between the followed solution strategy and the selected priority rule. For
example, students who thought that
the minimum cost solution would lie
in the neighborhood of the deadline
would adopt a more time-based strategy and select a priority rule that takes
into account activity durations. This
selection step does not reduce the subset of activities but accords a ranking to the activities; these rankings
serve as input for the intensity phase.
The priority rules used by the solution strategies are the Greatest Rank
Positional Weight (GRPW), Maximum
Slack (MAXSLK), and Average Most
Expensive Activity (the activity cost
divided by its duration) rules.
•;Intensity: Given the fact that students
have a limited amount of time to make
decisions, it is crucial to focus on the
most important activities. Intensity further selects activities by determining
a cut-off point for the ranked subset
that resulted from the previous phase.
A percentage between 0% and 100%
of the number of remaining activities
of the ranked subset is used as a value
for the intensity. This percentage is
multiplied by the number of elements
that are present in the ranked subset.
This subset then serves as input for
the action phase, where the trade-offs of
be altered, which corresponds with the
three general building blocks of heuris-
tics (Gigerenzer & Gaissmaier, 2011).
Search rules specify the direction of
the search space and are accounted
for by focus, activity criticality, ranking,
and intensity. Stopping rules determine
when the search process ends and is
governed by the time limit of the PSG.
Decision rules elaborate on how the
final decision is reached, which is done
by the fifth component, namely, action.
At the start of a decision moment,
every activity that has not started is
subject to a possible change. Out of this
group of activities, focus, activity criti-
cality, ranking, and intensity perform a
stepwise selection of a subset of activi-
ties. The process of stepwise selection
can be described as follows:
•;Focus: Specifies the length of the time
window during which actions will be
taken. All activities that start or are still
in progress during this time window
are selected. The focus is expressed as
a percentage of the number of decision
periods that are taken into account
and it can vary from a local to a global
orientation. A local orientation is char-
acterized by a narrow time window,
because the number of decision peri-
ods taken into account is small; at the
other end of the spectrum is a global
orientation, which uses a wide time
window. In this case, many activities
will be subject to a possible trade-off
•;Activity criticality: The subset of activities that start or are in progress during the time window specified by the
focus can be further refined based on
whether these activities are critical or
non-critical at the current decision
moment. If both critical and non-critical activities are taken into consideration, the subset of activities before
this phase equals the subset at the end
of the phase.
• Ranking: The elements of the subset
of activities are ranked based on the
value of a priority rule. Within the
context of human decision making,
Type of Action Description
Swap Select neighboring trade-off.
Slack consumption Increase duration until no slack is left.
Minimum cost slope Select trade-off with maximum duration decrease at minimum
Maximum revenue slope Select trade-off with minimum duration increase at maximum
Enumeration Enumerate all trade-off for set of activities.
Protect deadline Decrease/increase project duration until acceptable deviation
Table 3: Overview of the types of actions.