Guesstimation — ISB & IIMA Case Book Practice

Overview

Worked guesstimation problems from the ISB and IIMA case books, written to show reasoning rather than answers. Each problem states its assumptions openly, breaks the market into segments, builds the estimate bottom-up, then sanity-checks the result against a second angle to test whether the number is plausible.

Key takeaways

• Assumptions stated explicitly so the estimate can be challenged and adjusted.
• Top-down and bottom-up estimates cross-checked against each other.
• Structure and sanity checks prioritised over precision.

What's inside

• Problem decomposition approach
• Assumption tables
• Segment-level build-up
• Sanity checks and sensitivity