Question 1

What does cumulative percentage mean?

Accepted Answer

Cumulative percentage is the running total of individual percentages. If three items represent 20%, 35%, and 45% of a total, their cumulative percentages are 20%, 55%, and 100%. Each row adds the current percentage to all previous ones. The final entry always equals 100%.

Question 2

How is cumulative percentage used in Pareto analysis?

Accepted Answer

In Pareto (80/20) analysis, items are sorted by value (highest first). The cumulative percentage shows when you've covered 80% of the total effect. The items that appear before the 80% threshold are the "vital few" — they explain most of the outcome. This guides where to focus improvement efforts.

Question 3

What is the difference between cumulative percentage and cumulative frequency?

Accepted Answer

Cumulative frequency is the running count of data points (e.g., 5, 12, 18 items). Cumulative percentage converts that to percentages of the total count (e.g., 27.8%, 66.7%, 100%). They convey the same information, but percentage is scale-independent and allows comparison across datasets of different sizes.

Question 4

How do I sort data for cumulative percentage analysis?

Accepted Answer

For Pareto/ABC analysis: sort values from largest to smallest before calculating. This makes the cumulative curve steep initially and flat later, showing clearly which items dominate. For frequency distributions: sort data in natural order (e.g., age groups youngest to oldest) and the cumulative % shows "what percent of observations are at or below this value."

Question 5

What is ABC inventory classification using cumulative percentages?

Accepted Answer

Sort inventory items by value (annual spend or revenue). Calculate cumulative % of value. A items: top ~20% of items accounting for ~80% of value. B items: next ~30% of items, ~15% of value. C items: remaining ~50% of items, ~5% of value. The cumulative percentage column tells you exactly where A ends and B begins.

Question 6

Why doesn't my cumulative percentage reach exactly 100%?

Accepted Answer

This is a rounding issue. When individual percentages are rounded to fewer decimal places, they may not sum to exactly 100.00%. To fix: use more decimal places, or adjust the last row to make the cumulative total exactly 100%. In practice, a result of 99.99% or 100.01% due to rounding is acceptable.

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