Applications - Exam P formula sheet

Every Exam P formula in applications on one printable sheet, condensed from the 5 reference pages that teach them.

5 topics, 22 formula lines. Every line is condensed from the Exam P formula pages, which stay free to read in full. Print this page to get the sheet on paper; the site chrome drops away.

What is on this sheet

Applications

Transformations

CDF method
FY(y)=P(g(X)≤y)F_Y(y) = P(g(X)\le y)then differentiate
Monotone transform
fY(y)=fX(g−1(y))∣ddyg−1(y)∣f_Y(y) = f_X\big(g^{-1}(y)\big)\left|\dfrac{d}{dy}g^{-1}(y)\right|
Maximum of n iid
Fmax⁡(x)=[F(x)]nF_{\max}(x) = \left[F(x)\right]^{n}
Minimum of n iid
Smin⁡(x)=[S(x)]nS_{\min}(x) = \left[S(x)\right]^{n}
Convolution
fX+Y(s)=∫fX(x)fY(s−x) dxf_{X+Y}(s) = \int f_X(x)f_Y(s-x)\,dx

Deductibles and limits

Ordinary deductible
E[(X−d)+]=∫d∞S(x) dxE[(X-d)_{+}] = \int_d^{\infty} S(x)\,dx
Policy limit
E[X∧u]=∫0uS(x) dxE[X \wedge u] = \int_0^{u} S(x)\,dx
Decomposition
E[X]=E[X∧d]+E[(X−d)+]E[X] = E[X\wedge d] + E[(X-d)_{+}]
Exponential deductible
E[(X−d)+]=e−λdλE[(X-d)_{+}] = \dfrac{e^{-\lambda d}}{\lambda}memorylessness
Coinsurance
E[α(X−d)+]=αE[(X−d)+]E[\alpha(X-d)_{+}] = \alpha E[(X-d)_{+}]

Central limit theorem

Sum moments
E ⁣[∑Xi]=nμ,Var⁡ ⁣(∑Xi)=nσ2E\!\left[\sum X_i\right] = n\mu, \qquad \operatorname{Var}\!\left(\sum X_i\right) = n\sigma^{2}
Standardisation
Z=∑Xi−nμσn→dN(0,1)Z = \dfrac{\sum X_i - n\mu}{\sigma\sqrt{n}} \xrightarrow{d} N(0,1)
Sample mean
Xˉ≈N ⁣(μ,σ2n)\bar{X} \approx N\!\left(\mu, \dfrac{\sigma^{2}}{n}\right)
Continuity correction
P(S≥k)≈1−Φ ⁣(k−0.5−nμσn)P(S \ge k) \approx 1 - \Phi\!\left(\dfrac{k - 0.5 - n\mu}{\sigma\sqrt{n}}\right)

Repeated trials

Multinomial probability
P(N1=k1,…,Nm=km)=n!k1!⋯km! p1k1⋯pmkmP(N_1=k_1,\dots,N_m=k_m) = \dfrac{n!}{k_1!\cdots k_m!}\,p_1^{k_1}\cdots p_m^{k_m}
Marginals
Nj∼Binomial(n,pj)N_j \sim \text{Binomial}(n, p_j)
Covariance
Cov⁡(Ni,Nj)=−npipj,i≠j\operatorname{Cov}(N_i, N_j) = -n p_i p_j, \quad i \ne j
Constraint
∑jkj=n,∑jpj=1\sum_j k_j = n, \qquad \sum_j p_j = 1

Mixtures

Mixed density
f(x)=∑kwkfk(x),∑kwk=1f(x) = \sum_k w_k f_k(x), \qquad \sum_k w_k = 1
Mixed mean
E[X]=∑kwkμkE[X] = \sum_k w_k \mu_k
Mixed second moment
E[X2]=∑kwk(σk2+μk2)E[X^{2}] = \sum_k w_k\left(\sigma_k^{2} + \mu_k^{2}\right)
Variance
Var⁡(X)=∑kwk(σk2+μk2)−(∑kwkμk)2\operatorname{Var}(X) = \sum_k w_k\left(\sigma_k^{2}+\mu_k^{2}\right) - \left(\sum_k w_k\mu_k\right)^{2}