Bar (Gantt) charts in project control: Which of the following is an incorrect statement about Bar Charts used for planning and monitoring construction activities?
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AEach activity is generally represented by a single time-scaled bar.
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BBar charts establish the interdependency (logical precedence) of one event/activity on another.
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COnly an approximate percentage of the completed work is typically reported from a simple bar chart.
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DNone of these
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EBar charts are useful for communicating schedules to non-technical stakeholders
Answer
Correct Answer: Bar charts establish the interdependency (logical precedence) of one event/activity on another.
Explanation
Introduction / Context:Bar Charts (Gantt charts) are widely used for planning and progress reporting because they are simple and visually intuitive. However, they have limitations compared to network methods like CPM/PERT, especially in showing logical dependencies.
Given Data / Assumptions:
- Standard bar chart with activities plotted against time.
- No embedded network logic unless separately annotated.
- Construction project with multiple interdependent tasks.
Concept / Approach:Bar charts show duration and timing but not the full precedence network. Without additional notations (like arrows/links), they cannot reliably represent the interdependency of activities and events. Hence any statement claiming that bar charts inherently establish interdependency is incorrect.
Step-by-Step Solution:Evaluate Option A: A single bar per activity is the standard representation, so this is correct.Evaluate Option B: Claiming that bar charts establish interdependency is incorrect because pure Gantt formats lack explicit logical relationships.Evaluate Option C: Simple bar charts are commonly used to show approximate completion percentages, which is acceptable.Therefore, Option B is the incorrect statement.
Verification / Alternative check:Network diagrams (CPM/PERT) explicitly include nodes and links to show dependencies and critical paths; bar charts require extra linkage or a separate network to convey the same information.
Why Other Options Are Wrong:
- Option A: Accurately describes Gantt chart representation.
- Option C: Reflects typical practice of percent-complete reporting.
- Option D: 'None of these' is wrong because one statement is indeed incorrect.
- Option E: Bar charts are effective communication tools; this is true, but not central to the question.
Common Pitfalls:Confusing annotated Gantt charts (with precedence links) with basic bar charts; assuming visibility of float and criticality on bar charts without network analysis.
Final Answer:Bar charts establish the interdependency (logical precedence) of one event/activity on another.