Distributions Flashcards
1
Q
Discrete uniform distribution mean
A
(n-1) / 2
2
Q
Discrete uniform distribution variance
A
(n^2 - 1 ) / 12
3
Q
Binomial distribution formula, P(X=R) =
A
nCr p^r (1-p)^(n-r)
4
Q
When to use binomial formula?
A
Fixed number of trials
Fixed probability of success
Independent trials
Two outcomes, success/failure
5
Q
Point of inflection on a normal distribution
A
Mean +- standard deviation
6
Q
Percentages within standard deviations, normal distribution
A
68% within 1
95% within 2
99.7% within 3
7
Q
Z value and coding
A
Z varies N(0, 1^2)
Coding, Z = (y - mean)/s.d
8
Q
Approximating binomial as normal
A
If n is large and p is approx 0.5, u = np, s.d = root(npq)
9
Q
If approximating binomial as normal, use
e.g P(3<X<=11) =
A
Continuity correction, as changing from discrete to continuous.
P(3.5 < Y < 11.5)
