CAS common mistakes
CAS · Understand the traps and how to avoid them.
Writing a strategy answer that jumps straight to tactics (channel mix, posting cadence, budget splits) without first stating the business objective, target audience, and the single measurable goal the plan serves.
Candidates memorize channel playbooks and want to show breadth, so they front-load execution detail. Scenario stems often bury the objective in a sentence or two, and under time pressure it feels faster to describe what to do than to justify why.
What to do instead
Before writing, spend 60 seconds extracting three things from the stem: the business problem, the audience, and the success metric. Open every strategy response with a one-sentence objective statement and a measurable KPI, then map each tactic back to it. If a tactic cannot be tied to the stated goal, cut it.
Treating the target audience as a demographic label (for example, 'women 25-44') rather than defining the insight, need state, and buying trigger, then failing questions that ask for positioning or message strategy.
Demographic shorthand is the easiest thing to recall, and many candidates conflate an audience definition with an audience insight. Questions that probe positioning punish this because a demographic gives no basis for a differentiated message.
What to do instead
Practice converting every demographic into a need-based segment: what the person is trying to accomplish, what blocks them, and what would make them act now. In answers, state the segment, the insight, and the resulting positioning in that order so the logic is visible to the grader.
Confusing campaign objectives with media metrics, for example answering a brief that asks for awareness by proposing conversion-optimized performance tactics, or vice versa.
Real-world pressure to prove ROI makes candidates default to lower-funnel tactics regardless of the stated objective. Exam stems deliberately specify a funnel stage, and mismatched tactics read as not answering the question.
What to do instead
Build a mental mapping table: awareness pairs with reach and frequency metrics, consideration with engagement and assisted actions, conversion with CPA and ROAS. On every question, write the funnel stage in the margin first, then select only tactics and KPIs from that row.
Describing campaign management as a set of launch steps and omitting the optimization loop: what signals trigger a change, what is changed, and how the change is validated.
Launch checklists are easy to memorize and feel complete. Candidates rarely rehearse the mid-flight decision rules, so they describe setup and reporting but skip the intervention logic that campaign management questions actually test.
What to do instead
For any campaign management answer, include a short optimization cadence: review frequency, the threshold that triggers action, the specific lever pulled, and the guardrail metric watched to confirm no harm. Naming both the trigger and the guardrail is what separates a complete answer.
Computing reach and frequency or GRP questions by intuition instead of applying the formulas, and ignoring whether the question asks for average frequency versus effective frequency.
The arithmetic looks simple, so candidates skip writing it out and mis-multiply under time pressure. Average frequency and effective frequency are also easy to treat as synonyms, which flips the answer.
What to do instead
Write the formula before substituting numbers: impressions divided by reach gives average frequency, and GRPs equal reach percentage times average frequency. Distinguish effective frequency as the exposure count needed to move behavior, which is a planning judgment, not a computed output. Show the arithmetic so partial credit is possible.
Choosing media solely on CPM without addressing audience quality, context, viewability, or the cost of the outcome being purchased.
CPM is the most familiar efficiency number and is easy to compare across options. Candidates forget that a cheap impression delivered to the wrong audience or in a poor context is not efficient in outcome terms.
What to do instead
Evaluate every media option on at least three axes: cost efficiency (CPM or cost per point), audience fit (overlap with the target), and quality (viewability, brand safety, format). Where data allows, translate to cost per desired outcome. State explicitly why the chosen mix wins on outcome cost, not just on CPM.
Answering creative brief or production questions with subjective taste ('make it engaging') instead of tying creative decisions to the strategy, the single-minded proposition, and mandatory constraints such as format specs and legal clearance.
Creative evaluation feels like opinion, so candidates avoid committing to criteria. They also underweight production realities like aspect ratios, file weight limits, talent usage rights, and accessibility requirements.
What to do instead
Structure creative answers around a proposition, supporting reasons, and executional mandatories. Name the specific deliverable specs and clearance steps the scenario requires. When judging creative work, critique against the brief's objective and the audience insight rather than personal preference.
Reporting platform-attributed conversions as if they were incremental business results, and failing to flag overlap, double counting, or the difference between attribution models.
Dashboards present attributed conversions as clean totals, and candidates repeat them without interrogating what the model counts. Last-click bias and cross-platform overlap are conceptually understood but rarely applied in answers.
What to do instead
Whenever reporting results, state the attribution model in use, its known bias, and what it does not capture. Where incrementality matters, propose a control or holdout comparison. Distinguish platform-reported metrics from reconciled business outcomes and say which one the decision should rest on.
Building a budget answer as a flat percentage split across channels without showing the method: objective and task, historical benchmark, or test-and-scale logic, and without a contingency reserve.
Percentage splits are quick to produce and look decisive. Candidates skip the derivation because it takes more words, and they omit reserves and scenario ranges because the stem does not explicitly ask for them.
What to do instead
Name the budgeting method you are using and why it fits the scenario, then show the arithmetic from objective to spend. Include a reserve line and a range (base, upside, downside) so the plan survives variance. Close with the ROI or payback threshold that would justify continuing the spend.
Handling ethics and compliance questions by asserting that something is 'best practice' or 'allowed' without citing the governing principle, the disclosure requirement, or the data-permission basis.
Candidates rely on general impressions of what feels acceptable and avoid committing to rules they are unsure of. Compliance stems often hinge on a specific requirement such as consent basis, clear disclosure of paid content, or substantiation of claims.
What to do instead
For each ethics or compliance scenario, identify the obligation category first: claim substantiation, disclosure of material connections, data consent and use limitation, or vulnerable-audience protection. Then state the specific action required and the risk of not taking it. Anchor answers in principles and documented permission rather than in vague appeals to best practice.