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Stretch: Isla Mobile: should it launch a weekly data pass?
You run the case. Read the prompt, answer questions from the notes below, and share data only when the candidate asks for it or gets stuck. Score at the end.
Case timer
00:00
1. Read the prompt aloud
Read it slowly, then pause. Let the candidate ask questions before they structure.
Isla Mobile, a mobile operator in the Philippines, sells prepaid data mostly as daily passes. It is considering a weekly pass at PHP 99. Using the table below, would the weekly pass raise data revenue, and at what price?
The prompt refers to Exhibit 1. After reading it, say: "Open Exhibit 1 now."
Format note: Difficulty: Stretch. Format: interviewer-led, with an exhibit. Industry: Telecom. Region: Philippines. Interview length: about 35 minutes. The company is fictional and all figures are illustrative.
2. Answers to clarifying questions
Give these answers only if the candidate asks. If they ask something not listed, give a sensible answer or say it does not matter here.
If asked: How do prepaid users buy data today?
Answer: With a daily pass of PHP 20 for 1 GB. The exhibit shows the segments (illustrative).
If asked: What is the new product?
Answer: A weekly pass of PHP 99 with 7 GB.
If asked: Who would buy it?
Answer: Market research suggests every heavy daily buyer would switch, 25 percent of light daily buyers would switch, and 2 percent of prepaid users who buy no pass today would start (illustrative).
3. The hypothesis a strong candidate states
Listen for an early, testable guess like this one. It does not need to match word for word.
A weekly pass gives heavy users a discount and asks light users to spend more. My hypothesis is that it pays only if enough light users and new users take it to make up for heavy users paying less.
4. A model structure
Compare the candidate's structure with this one. A different split can be just as good if it is clean and fits the problem.
- Change in weekly revenue = gains from upgraders and new buyers - losses from heavy users
- Key: Heavy daily buyers who switch and pay less
- Light daily buyers who switch and pay more
- New buyers among prepaid users with no pass
- Price: test a higher weekly price
Exhibit 1
The prompt uses this exhibit, so the candidate opens it right after you read the prompt ("Show exhibit 1" on their screen).
| Segment | Users (million) | Daily passes a week | Weekly spend (PHP) |
|---|---|---|---|
| Light daily-pass buyers | 4 | 3 | 60 |
| Heavy daily-pass buyers | 2 | 6 | 120 |
| Prepaid users with no pass | 14 | 0 | 0 |
So-what
Heavy buyers already spend PHP 120 a week, more than the planned PHP 99 pass, so each heavy buyer who switches pays less.
5. The working, step by step
Each step shows how a strong candidate works it out. Share a new fact from it only when the candidate asks or is stuck, and let them do the math: the result in the dark box is what they should reach.
Step 1: Pass revenue today
What a strong candidate does: Light buyers: 3 passes a week at PHP 20. Heavy buyers: 6 passes a week.
Weekly pass revenue today (PHP): 4,000,000 × 3 × 20 + 2,000,000 × 6 × 20 = 480,000,000
Step 2: Heavy buyers switch
What a strong candidate does: Each heavy buyer now pays PHP 99 instead of PHP 120 a week.
Change from heavy buyers (PHP a week): 2,000,000 × (99 - 6 × 20) = -42,000,000
Step 3: Light buyers switch
What a strong candidate does: A quarter of light buyers pay PHP 99 instead of PHP 60 a week.
Change from light buyers (PHP a week): 4,000,000 × 0.25 × (99 - 3 × 20) = 39,000,000
Step 4: New buyers
What a strong candidate does: 2 percent of the users who buy no pass today start buying the weekly pass.
Revenue from new buyers (PHP a week): 14,000,000 × 0.02 × 99 = 27,720,000
Step 5: Net change at PHP 99
What a strong candidate does: The three effects together.
Net change in revenue at PHP 99 (PHP a week): 2,000,000 × (99 - 6 × 20) + 4,000,000 × 0.25 × (99 - 3 × 20) + 14,000,000 × 0.02 × 99 = 24,720,000
Step 6: Curveball: price it at PHP 119
What a strong candidate does: Interviewer: "Research says that at PHP 119 heavy buyers still all switch, but only 15 percent of light buyers and 1.5 percent of non-buyers take it." Net weekly change at PHP 119:
Net change in revenue at PHP 119 (PHP a week): 2,000,000 × (119 - 120) + 4,000,000 × 0.15 × (119 - 60) + 14,000,000 × 0.015 × 119 = 58,390,000
Step 7: A year at PHP 119
What a strong candidate does: Over 52 weeks.
Yearly gain at PHP 119 (PHP): (2,000,000 × (119 - 120) + 4,000,000 × 0.15 × (119 - 60) + 14,000,000 × 0.015 × 119) × 52 = 3,036,280,000
The recommendation to listen for
At the end, say: "The CEO walks in. What is your recommendation?"
Launch the weekly pass, but at PHP 119 rather than PHP 99. First, at PHP 99 heavy buyers switch and pay PHP 21 less each week, costing about PHP 42 million a week, which light upgraders and new buyers only just outweigh, for a net gain of about PHP 25 million a week. Second, at PHP 119 heavy buyers lose only PHP 1 each, and even with fewer light and new buyers the gain rises to about PHP 58 million a week, or about PHP 3 billion a year. Third, the gain depends on new and light users, whose response is the least certain number, so test before a national launch. Launch at PHP 119 in two regions for a month, compare take-up with the research, and watch network load, since weekly passes invite heavier use.
Risks a strong answer names: Rivals may launch a cheaper weekly pass; Heavier data use on weekly passes may need more network capacity.
Next steps: Run the two-region test with a control region; Measure the share of light buyers who switch at each price.
Strong versus weak
A strong answer
Split the effect by segment, saw that heavy users pay less, sized each group, and used the curveball to find a better price.
A weak answer
Multiplied 20 million users by PHP 99 and called it a large new revenue stream, ignoring the revenue that heavy buyers already bring.
Score the candidate
Score each criterion from 1 to 5. A 2 or a 4 sits between the descriptions.
Total
0 out of 25
Score all five criteria to see the band and the feedback template.