Praxis — An adaptive tutor that shows its working Guest learner

Probability & Statistics › Distributions

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Numeric Moderate empirical-rulenormal ~60s

Scores are normally distributed with mean 100 and standard deviation 15. Approximately what percentage of scores fall between 85 and 115? Give a whole number.

Fractions, decimals and π are all understood.

Hints are free to take and they are counted. A correct answer after two hints moves your mastery less than one without — which is the honest way to score it.

Why this question? this skill is new to you; it stretches you slightly; and it needs calibrating — few people have tried it Predicted chance you get it: 48% — the selector aims at 78%.
difficulty fit 0.036
skill need 0.75
review boost 0
calibration bonus 0.12
recency penalty 0
repetition penalty 0
frustration 0