Normal probabilities and inverse normal
Practice Flashcards
Flip to reveal answersWhat does X ~ N(μ, σ²) mean?
Track your progress — Sign up free to save your progress and get smart review reminders based on spaced repetition.
All 9 Flashcards — Normal probabilities and inverse normal
Sign up free to track progress and get spaced-repetition review schedules.
Question
What does X ~ N(μ, σ²) mean?
Answer
X is normally distributed with mean μ and variance σ² (so standard deviation σ).
Question
What shape is the normal distribution?
Answer
A symmetric bell curve centred on the mean.
Question
What does normalcdf(lower, upper, μ, σ) give?
Answer
The probability P(lower < X < upper) — the area under the curve between the bounds.
Question
How do you find P(X < a) on the GDC?
Answer
normalcdf with a very small lower bound (e.g. −1E99) and upper bound a.
Question
How do you find P(X > a)?
Answer
normalcdf with lower bound a and a very large upper bound (e.g. 1E99).
Question
What is P(X < μ)?
Answer
0.5 — half the area is below the mean.
Question
State the 68–95–99.7 rule.
Answer
About 68% of data lies within 1σ of the mean, 95% within 2σ, 99.7% within 3σ.
Question
How do you find an expected number from a normal probability?
Answer
Multiply the probability (normalcdf) by the total number of items.
Question
In N(150, 20²), what is σ?
Answer
20 (the variance is 400; the GDC needs σ = 20).
Read the notes
Full study notes for Normal probabilities and inverse normal
Topic 4.9 hub
Normal distribution
More from Topic 4.9
All flashcards in this topic
Math AA exam skills
Paper structures & tips
Track your progress with spaced repetition
Sign up free — Aimnova tells you exactly which cards to review and when, so you remember everything before your IB exam.
Start Free