Quantitative skills in business common mistakes

Common mistakes

• Misinterpreting the sign of a percentage change

  Assuming a negative change always means a loss in value

  Fix itA negative percentage indicates a decrease relative to the original value, not necessarily a loss in absolute terms.

• Confusing average with median

  Assuming the middle value of a data set is the average.

  Fix itThe average is the sum of all values divided by the number of values, not the middle value.

• Confusing revenue with profit

  Assuming revenue equals profit.

  Fix itRevenue is the total sales income; profit is revenue minus total costs, including both variable and fixed costs.

• Confusing gross profit margin with net profit margin

  Assuming gross profit margin includes all costs.

  Fix itGross profit margin only considers the cost of goods sold; net profit margin includes all operating expenses, interest and tax.

• Confusing average rate of return with simple return

  Assuming the average rate of return is the same as the simple return over a single period.

  Fix itThe average rate of return takes the total net profit over the investment period and divides it by the initial investment, then multiplies by 100 to give a percentage.

• Confusing profit with cash flow

  Assuming that profit equals cash flow.

  Fix itProfit is accounting income after expenses, while cash flow is the actual cash movement; they can differ due to timing and non‑cash items.

• Misreading the Y‑axis scale

  Assuming the Y‑axis starts at zero when it does not.

  Fix itAlways check the minimum value on the Y‑axis; if it starts above zero, the visual impact of differences may be exaggerated.

• Confusing gross profit margin with gross profit

  Assuming a 40% gross profit margin means the company makes £40 profit on every £100 of sales.

  Fix itThe 40% figure represents the proportion of revenue that is gross profit; the actual gross profit is revenue multiplied by 40%.

• Confusing revenue with profit

  Assuming that the total sales figure is the same as the profit.

  Fix itRevenue is the total sales income; profit is revenue minus all costs. Always look for the net profit line on a profit and loss statement.

• Confusing market size with market share

  Thinking that the total number of customers in a market equals a company’s market share.

  Fix itMarket size is the total number of customers or total sales in the market. Market share is the portion of that market that a specific company or brand captures.