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2.2.2 Examples of Linear Combinations of Random Variables

Example 1: Total Cost of Production

  • Situation: Calculating the total cost of a product based on material and labor costs, both of which are random variables.
  • Random Variables:
  • X1: Units of material used (random)
  • X2: Units of labor used (random)
  • Linear Combination: image

  • a1​, a2: Per-unit costs of material and labor, respectively.

  • Result: Y represents the total cost, influenced by the random quantities of material and labor.

Example 2: Total Monthly Profit of a Retail Chain

  • Situation: A retail chain operates several stores; monthly sales at each are random.
  • Random Variables: image
    Monthly sales in units at each of n stores.
  • Linear Combination: image

  • image
    Profits per unit sold in each store.
  • Result: Y represents the total monthly profit across all stores, combining individual profits adjusted by sales volumes.

Example 3: Total Monthly Expenses of a Business

  • Situation: A company incurs monthly expenses in various categories like personnel, marketing, etc., each being a random variable due to fluctuating costs.
  • Random Variables: image
    Expenditures in each category.
  • Linear Combination: image

  • Result: Y represents the total monthly expense of the business, aggregating all categorical expenses.


Example 4: Average Sales Commission

  • Situation: Sales commissions are collected by different sales reps, each commission being a random variable.
  • Random Variables: image
    Commissions collected by n sales reps.
  • Linear Combination: image

  • Result:
    Y is the average sales commission per sales rep for that month.

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