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Management Accounting · Sources of data

Data Collection Methods and the Cost-Benefit of Information

Updated 11 October 2026 · Fact-checked

Data collection methods are the ways you gather facts: surveys, questionnaires, interviews, observation and existing records. Each has a cost and a quality. Information is worth collecting only if its expected benefit, through better decisions, is greater than the cost of getting it. In the exam, match method to need, then compare cost and benefit.

Understand Data Collection Methods and Cost-Benefit of Information

Management accountants need data before they can produce information. Data can come from inside the business, such as sales records, or from outside, such as market reports. When the data does not already exist, you must collect it yourself. This is primary data. Using data that someone else already collected is secondary data.

The main primary methods are these:
- Questionnaires: a fixed set of written questions sent to many people. Cheap per person and easy to compare, but response rates can be low and you cannot probe answers.
- Interviews: a conversation, face to face or by phone. You can ask follow-up questions and get detail, but they are slow, costly and the interviewer can bias answers.
- Observation: you watch what people actually do, such as timing a task. It shows real behaviour, but people may act differently when watched.
- Surveys: a wider term for collecting data from a sample or population, often using questionnaires or interviews.

A good questionnaire uses clear, short and neutral questions. Avoid leading questions that push the answer, and avoid questions that ask two things at once. Use closed questions (tick a box) for easy analysis and a few open questions for detail. Put easy questions first, keep it short, and test it on a small group (a pilot) before the full launch. Choose who to ask carefully, because a poor sample gives misleading results.

Information has a cost: time, staff, payments, systems and delay. It also has a benefit: better decisions, lower risk, saved costs or extra revenue. The rule is simple. Collect more information only while its benefit exceeds its cost. Benefits are often hard to measure, so costs are usually clearer than benefits. Perfect information is rarely worth paying for.

Big data means very large, fast-growing and varied sets of data, such as website clicks, social media, card transactions and sensor readings. Businesses analyse it to spot patterns, target customers and forecast demand. Its limits are cost of storage and analysis, data quality, privacy rules and the risk of finding patterns that mean nothing.

Key formulas to remember

Cost-benefit rule for information
Net benefit of information = Expected benefit − Cost of obtaining it
Collect or buy the information only if the net benefit is positive.
Value of information (expected value)
Value of information = Expected value with the information − Expected value without it
Compare this value with the cost. If cost is lower, the information is worth buying.
Response rate
Response rate = Responses received ÷ Questionnaires sent × 100%
A low rate raises the risk of non-response bias.
Cost per response
Cost per response = Total collection cost ÷ Responses received
Useful for comparing methods such as postal questionnaires and interviews.

How to solve Data Collection Methods and Cost-Benefit of Information questions

Use this method for any question on collection methods or the cost and benefit of information.

  1. 1Read the question and identify what decision or purpose the data will serve.
  2. 2Decide if the data is already available (secondary) or must be collected (primary).
  3. 3List the candidate methods and note the key strength and weakness of each: cost, speed, depth, bias, response rate.
  4. 4Match the method to the need. Large sample and low cost point to questionnaires. Detail and probing point to interviews. Real behaviour points to observation.
  5. 5For design questions, check wording: clear, neutral, one idea per question, sensible order, tested by a pilot.
  6. 6For cost-benefit questions, work out the total cost and the expected benefit in the same units and time period.
  7. 7Subtract cost from benefit and state whether the information is worth obtaining.
  8. 8Read all four options before selecting, and check how many answers the question asks for.

Quickest way: Match, then compare

When to use it: Use this for multiple choice and multiple response questions where time is short.

  1. Underline the need in the question: cheap, detailed, large sample, real behaviour or fast.
  2. Eliminate options that contradict the need, such as interviews for a cheap, large sample.
  3. For cost-benefit numbers, compute benefit minus cost once and check the sign.
  4. Check for traps: leading questions, double-barrelled questions, or costs that are not relevant.
  5. Pick the answer that fits the need, not the one that is merely true.

Common mistakes in Data Collection Methods and Cost-Benefit of Information

  • Saying questionnaires give detailed, in-depth answers.

    Students confuse them with interviews.

    Fix: Remember that questionnaires are cheap and wide but shallow. Interviews are deep but costly and slow.

  • Accepting a leading question as good design.

    The wording sounds polite, so the bias is missed.

    Fix: Ask whether the wording suggests a preferred answer. If it does, it is leading and poor.

  • Ignoring the cost of information in cost-benefit questions.

    Students focus on how useful the data is.

    Fix: Always subtract the cost from the benefit. Useful information can still be not worth its cost.

  • Treating a high-benefit item as worth buying without comparing the cost.

    Students stop after finding the benefit figure.

    Fix: Compare benefit with cost and decide only on the net figure.

  • Confusing primary and secondary data.

    Both are used in the same project, so the labels blur.

    Fix: Primary means you collected it for this purpose. Secondary means it already existed.

  • Claiming big data is always accurate because it is large.

    Size is mistaken for quality.

    Fix: State that big data still needs checking for quality, relevance, privacy and cost of analysis.

Worked examples

Example 1

A company can pay $6,000 for a market survey. Without it, the expected profit from launching a product is $40,000. With the survey, the expected profit is $44,500 before paying for the survey. Is the survey worth buying?

Show the solution
  1. Value of the information = $44,500 − $40,000 = $4,500.
  2. Cost of the survey = $6,000.
  3. Net benefit = $4,500 − $6,000 = −$1,500.

Answer: The survey is not worth buying. Its cost exceeds the value of the information by $1,500.

Example 2

A firm sends 800 questionnaires and receives 200 replies. The total cost is $1,000. Calculate the response rate and the cost per response.

Show the solution
  1. Response rate = 200 ÷ 800 × 100% = 25%.
  2. Cost per response = $1,000 ÷ 200 = $5.

Answer: The response rate is 25% and the cost per response is $5.

Exam tips

  • Link every method to its main weakness. Exams often ask for the drawback, not the benefit.
  • In design questions, look for leading, vague or double-barrelled wording and rule those options out.
  • For number entry, show the subtraction of cost from benefit and check the sign of your answer.
  • In multiple response questions, select exactly the number asked and no more.
  • Use the words primary, secondary, cost, bias and response rate. They match how the examiner frames options.

Practice questions from Sources of data

Data Collection Methods and Cost-Benefit of Information in other exams

The same ground in other exams, if you are preparing for more than one or want another angle on it.

Data Collection Methods and Cost-Benefit of Information: frequently asked questions

What is the difference between a questionnaire and an interview?

A questionnaire is a written set of fixed questions, usually sent to many people at low cost. An interview is a conversation where you can ask follow-up questions. Interviews give more depth but cost more and take longer.

How do I design a good questionnaire?

Keep it short and use clear, neutral wording with one idea per question. Mix mostly closed questions with a few open ones, order them logically and test it on a small group first. This reduces errors and improves the response rate.

How do I judge whether information is worth its cost?

Estimate the benefit it brings, such as better decisions or saved costs. Then subtract the cost of getting it. If the result is positive, the information is worth obtaining.

What is big data in management accounting?

Big data is very large and varied data, such as web activity, transactions and sensor readings. Accountants use it to understand customers, costs and demand. It is limited by cost, data quality and privacy concerns.