The identity used by Basic Probability
For a finite equally likely sample space, event probability is favorable outcomes divided by all possible outcomes. The result lies from zero through one.
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Basic Probability Calculator
Divide favorable outcomes by total equally likely outcomes. Formula and event probability remain visible in one place for independent verification.
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A scratch-paper check for Basic Probability
Define nonoverlapping elementary outcomes, count the complete sample space, count those satisfying the event, and divide.
Seven favorable outcomes among twenty equally likely possibilities give 7/20=0.35, or 35%. This Basic Probability example can be compared with observed frequency.
Questions Basic Probability can resolve
Rework Basic Probability without copying Event probability. Begin with Favorable outcomes and preserve Total outcomes. Predict the scale of the Basic Probability answer, then compare it with Event probability. Store a changed Total outcomes as another Basic Probability case.
This model handles fair dice, shuffled cards, random selections, and other settings where each elementary outcome has equal weight.
Keeping a usable Basic Probability record
How to label a Basic Probability result
Start the Basic Probability review with Favorable outcomes. Compare Favorable outcomes with its source, then test Total outcomes in a second Basic Probability run without changing the first Basic Probability case.
Counting alone is insufficient when outcomes have unequal probabilities. Favorable outcomes cannot exceed the total and the sample space cannot be empty. If the Basic Probability assumptions do not fit, consider opposite event.
Reproducing Basic Probability
A reproducible Basic Probability record contains Favorable outcomes, Total outcomes, the selected calculation mode, and the final rounding rule. Keep decimals on the zero-to-one scale during probability arithmetic and label any percentage conversion separately. Exact counting results should remain integers even when they are very large.
For Basic Probability, for an independent check, simplify the setup by removing one stage or fixing one object. The smaller result should relate to the original through a known factor, coefficient, or complement rather than through coincidence.
Cross-checking Basic Probability
Work backward from the displayed Event probability once. Ask whether Favorable outcomes can produce that Event probability under Total outcomes. If the reverse Basic Probability relationship fails, recheck the entry order and any convention attached to Total outcomes.
Validating Basic Probability
Challenge Event probability with a nearby value of Favorable outcomes. Leave Total outcomes fixed during the Basic Probability trial. The direction of the new Event probability should agree with the underlying Basic Probability relationship.
Questions about Basic Probability
Must outcomes be equally likely?
Yes for this counting ratio.
Can probability exceed one?
No.
What does probability zero mean?
The event is impossible within the stated model.
How is a percentage obtained?
Multiply the decimal probability by 100.