Posted by **Lori** on Sunday, September 26, 2010 at 6:47pm.

A student takes a 20-question, true/false exam and guessed on each question. Find the probability of passing if the lowest passing grade is 15 correct out of 20.

- statistics -
**PsyDAG**, Monday, September 27, 2010 at 12:31pm
What you want to know is the chance probability of obtaining 15, 16, 17, 18, 19, or 20 correct.

Prob. of 15 = .5^15...

Prob. of 20 = .5^20

Either-or probability = sum of individual probabilities.

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