gyankalakumbhKNOWLEDGE. ART. POSSIBILITY.Logic & puzzles • Classes 9–12
Count before trusting a percentage
A high success rate can hide the size of the groups.
Take your time. Speak, draw or write your answers.
Here is what is happening.
Percentages need denominators. In an example sorting task, 90 out of 100 ordinary cards and 1 out of 2 rare cards are labelled correctly. Combining the counts gives 91 out of 102, but this overall result hides weaker performance for rare cards. Look at both totals and subgroups.
Pause. Make the idea your own.
Explain one idea to a partner, draw it or write it in your own words. Which part is an observation, an example or a question?
You can use a home language. No need to share personal experiences or finish everything in one sitting.Your little investigation
What you need
Paper and a pencil, or a partner to talk with. Drawing and speaking are welcome.
Draw separate tables for ordinary and rare cards.
Calculate 90/100 and 1/2 as percentages.
Explain why “the system is good overall” may be incomplete for rare cases.
What is accuracy on the two rare cards?
KEEP ASKING
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