Formulas for AP Statistics
I. Descriptive Statistics
1 ∑ xi 1 ∑ ( xi − x )2
x = ∑ xi = sx = ∑ ( xi − x )2 =
n n n −1 n −1
ŷ = a + bx y = a + bx
x − x yi − y sy
∑ i
1
r = b=r
n − 1 s x s y sx
II. Probability and Distributions
P ( A ∩ B)
P ( A ∪ B ) = P ( A) + P ( B ) − P ( A ∩ B ) P ( A | B) =
P ( B)
Probability Distribution Mean Standard Deviation
µ X = E ( X ) = ∑ xi P ( xi )
σ X = ∑ ( xi − µ X ) P ( xi )
2
Discrete random variable, X
If 𝑋𝑋 has a binomial distribution
with parameters n and p, then:
µ X = np σ X = np (1 − p )
n
P ( X = x ) = p x (1 − p )n − x
x
where x = 0, 1, 2, 3, , n
If 𝑋𝑋 has a geometric distribution
1 1− p
with parameter p, then: µX = σX =
p p
P ( X = x ) = (1 − p ) x −1 p
where x = 1, 2, 3,
III. Sampling Distributions and Inferential Statistics
statistic − parameter
Standardized test statistic:
standard error of the statistic
Confidence interval: statistic ± ( critical value )( standard error of statistic )
( observed − expected )2
Chi-square statistic: χ 2 = ∑ expected