The contractor sends a report: clicks cost 100 ₸, and app installs are cheap too. The owner wants to increase the budget but does not yet know how much the orders contribute after costs. The marketer needs to carry the calculation through to the purchase and explain where the available evidence ends.
The numbers are illustrative. The shop and the app are separate problems with their own assumptions. Write down your calculations before reading the explanations: this is a written self-assessment with no automatic score.
Problem 1: the shop's cost per customer
A campaign generated 500 clicks at 100 ₸ each. Of those clicks, 2% became leads, and 10% of leads became new paying customers. In this problem, each person submitted at most one lead and made one purchase. The agreed period for processing leads has ended.
An order is worth 50,000 ₸. After the variable costs of the goods and fulfilment, 30% of revenue remains before advertising. No other costs are specified.
Calculate ad spend, leads, buyers, the ad-only cost per new customer and the contribution of the first order after advertising. Then write one sentence about the result for the owner. Separately, identify the missing information needed to assess the business over a longer period.
Problem 2: an install or a useful action
A different project compares two mobile campaigns over the same period. Every user has had seven full days since installation. The team defines activation as a first useful action, with the same definition for both groups. Repeating the action does not add another activated user.
| Metric | Campaign A | Campaign B |
|---|---|---|
| Ad spend | 100,000 ₸ | 150,000 ₸ |
| Installs | 1,000 | 500 |
| Users activated within 7 days | 100 | 150 |
Calculate CPI, the activation rate and the cost per activated user. The manager proposes keeping only B because its activation rate is higher. Is the information sufficient for that decision? Name the next outcome you would request from the app team.
Problem 3: a new creative increased CTR
CTR increased after an ad was replaced. Someone wants the report to say, “The new creative generates more profit,” although spend, payments and refunds have not yet been reconciled.
Describe the observation, the data needed for an economic conclusion and a way to distinguish the creative's effect from other changes. Your answer should include a next check that an analyst or media buyer can perform.
Shop explanation: follow both conversion steps
The clicks cost 500 × 100 = 50,000 ₸. They generated 500 × 2% = 10 leads. Of those, 10 × 10% = 1 person paid. The ad-only cost per new customer is 50,000 / 1 = 50,000 ₸.
Another figure in the calculation is 5,000 ₸: 50,000 / 10, the cost per lead. Labelling it CAC would erase the nine leads that did not pay. Each metric needs its own denominator.
The first order contributes 50,000 × 30% = 15,000 ₸ before advertising. After advertising, the result is 15,000 - 50,000 = -35,000 ₸. Variable costs have already been deducted to calculate contribution. Subtracting the cost of the goods from that 15,000 ₸ again would count it twice.
The owner could receive this explanation: “The first order contributed 15,000 ₸ against 50,000 ₸ in ad spend, so it did not cover that spend within this period.” This is the first order's contribution after advertising. Full CAC would also include other agreed acquisition costs absent from the problem, and the company's financial result includes other expenses.
A longer horizon requires repeat purchases from this same group, their contribution, refunds, retention costs and the timing of receipts. A planned reminder is not a reason to include a future purchase in the actual result. If there has not been enough time for repeat orders, show the current result separately from a scenario with explicit assumptions.
App explanation: the same cost per activation
An install costs 100,000 / 1,000 = 100 ₸ in A and 150,000 / 500 = 300 ₸ in B. Activation rates are 100 / 1,000 = 10% and 150 / 500 = 30%.
| Metric | Campaign A | Campaign B |
|---|---|---|
| CPI | 100 ₸ | 300 ₸ |
| Activation within 7 days | 10% | 30% |
| Cost per activated user | 1,000 ₸ | 1,000 ₸ |
B has three times the cost per install and three times the activation rate. The cost per activated user is equal: both 100,000 / 100 and 150,000 / 150 give 1,000 ₸. Choosing on CPI alone misses the quality of the next step; choosing on activation rate alone misses the spending.
The next request is for purchases and contribution from those same groups over equal, completed observation windows. The useful action may be close to a purchase, but its definition still needs to reflect the user's task. Comparable audiences and consistent rules for attributing outcomes to campaigns also matter.
Even if one current group has better economics, moving the whole budget needs further justification. Additional spending may reach a different audience and change the cost of the next buyer. The report can propose a limited budget increase with an evaluation plan, rather than promise the same cost at any volume.
Creative explanation: distinguish the observation from its cause
CTR rose: the data under review has more clicks per impression. An economic calculation needs spend, new buyers, paid orders, variable costs and refunds over an agreed period. Those records must describe one comparable group, rather than combine a week's clicks with every shop sale in a month.
A before-and-after comparison leaves other explanations open: the audience, bids, offer or timing. The analyst can first compare settings and group composition, then propose an experiment that isolates the creative change. Plan the data volume around an effect large enough to change the team's decision. The single buyer in the first problem permits an exact calculation of money already spent, but offers too little evidence for a confident forecast of the next campaign.
Exercise: a calculation for your own report
Choose one acquisition source in your project and an agreed period. Create a row containing spend, leads, new buyers and the contribution of their first orders. State the included costs, the deduplication rule and the time allowed for payment. Leave missing data blank and name the person who can supply the export.
For a numerical check, change just one shop assumption: 20% of the ten leads now pay, while everything else stays the same. Recalculate the result and explain what you can now tell the owner.
Two people paid. The ad-only cost per customer fell to 50,000 / 2 = 25,000 ₸, and total contribution before advertising rose to 2 × 15,000 = 30,000 ₸. After advertising, the result is -20,000 ₸. It improved by 15,000 ₸, but the first orders still failed to cover the spend.
Your project's explanation should make the same connection between source records and the conclusion. If payments are still maturing or contribution is unknown, leave that part unresolved. The reader should be able to tell which calculation is complete and what information the next decision requires.