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Further Statistics 1 formulae

The 16 results the Further Statistics 1 notes display, each with the conditions it needs to be true and a link to the lesson that states it. Of the 16, the formulae booklet prints 13 and 3 are yours to memorise.

Further Maths · 7 lessons with formulae.

A result the Edexcel formulae booklet prints is marked as such; one it does not print is marked to learn; and a result badged derived in the lesson is a working line the notes build in front of you rather than a standard result to memorise.

7 lessons

Discrete random variables and expectation

E(X)=ΣxP(X=x)\text{E}(X) = Σ \, x \, \text{P}(X = x)IN THE FORMULAE BOOKLETConditionsX discrete, summed over every value in its range, and the sum must converge.
Var(X)=Σx2P(X=x)-μ2\text{Var}(X) = Σ \, x^{2} \, \text{P}(X = x) - μ^{2}IN THE FORMULAE BOOKLETConditionsX discrete with μ = E(X), and E(X²) must exist.
E(X)=n+12,Var(X)=n2-112\text{E}(X) = \frac{n + 1}{2}, \qquad \text{Var}(X) = \frac{n^{2} - 1}{12}NOT IN THE BOOKLET: LEARN ITConditionsA discrete uniform distribution on the values 1 to n, every one equally likely. A list that is uniform but does not run 1 to n needs the sums done over its own values.

The Poisson distribution

P(X=x)=e-λλxx!,E(X)=Var(X)=λ\text{P}(X = x) = e^{-λ} \frac{λ^{x}}{x!}, \text{E}(X) = \text{Var}(X) = λIN THE FORMULAE BOOKLETConditionsEvents occurring singly, independently and at a constant average rate λ > 0; x = 0, 1, 2, …

Geometric and negative binomial distributions

P(X=x)=p(1-p)x-1,μ=1p,σ2=1-pp2\text{P}(X = x) = p(1 - p)^{x-1}, μ = \frac{1}{p}, σ^{2} = \frac{1 - p}{p^{2}}IN THE FORMULAE BOOKLETConditionsIndependent trials with constant p, 0 < p ≤ 1, X counting the trial of the first success; x = 1, 2, 3, …
P(X=x)=x-1Cr-1pr(1-p)x-r\text{P}(X = x) = \, ^{x-1}C_{r-1} \, p^{r}(1 - p)^{x-r}IN THE FORMULAE BOOKLETConditionsIndependent trials with constant p, X counting the trial of the rth success; x = r, r + 1, …
μ=rp,σ2=r(1-p)p2μ = \frac{r}{p}, σ^{2} = \frac{r(1 - p)}{p^{2}}IN THE FORMULAE BOOKLETConditionsThe negative binomial above, with p > 0.

The Central Limit Theorem

sample mean≈N(μ,σ2n)\text{sample mean} \approx \text{N}(μ, \frac{σ^{2}}{n})IN THE FORMULAE BOOKLETConditionsA random sample of n independent, identically distributed observations with a finite mean and variance, and n large. The parent distribution need not be normal.

Goodness-of-fit tests

χ2=Σ(Oi-Ei)2Eiχ^{2} = Σ \frac{(O_{i} - E_{i})^{2}}{E_{i}}IN THE FORMULAE BOOKLETConditionsExpected frequencies all at least 5, pooling classes where they are not, and the observations independent.

Contingency tables

Eij=row total×column totalgrand totalE_{ij} = \frac{\text{row total} × \text{column total}}{\text{grand total}}NOT IN THE BOOKLET: LEARN ITConditionsComputed under the null hypothesis that the two classifications are independent; each expected frequency should be at least 5.
χ2=Σ(Oi-Ei)2Eiχ^{2} = Σ \frac{(O_{i} - E_{i})^{2}}{E_{i}}IN THE FORMULAE BOOKLETConditionsExpected frequencies all at least 5, pooling classes where they are not, and the observations independent.
χ2=Σ(|O-E|-0.5)2Eχ^{2} = Σ \frac{(|O - E| - 0.5)^{2}}{E}NOT IN THE BOOKLET: LEARN ITConditionsYates' correction, for a contingency table with two rows and two columns and therefore one degree of freedom; expected frequencies at least 5. A larger table takes the uncorrected statistic.

Probability generating functions

G(t)=E(tX)=ΣtxP(X=x)\text{G}(t) = \text{E}(t^{X}) = Σ \, t^{x} \, \text{P}(X = x)IN THE FORMULAE BOOKLETConditionsX taking non-negative integer values, with the series convergent, which it is for |t| ≤ 1.
Var(X)=G′′(1)+G′(1)-[G′(1)]2\text{Var}(X) = \text{G}''(1) + \text{G}'(1) - [\text{G}'(1)]^{2}IN THE FORMULAE BOOKLETConditionsG differentiable twice at t = 1, so the mean and variance must exist.
B(n,p):(q+pt)n,Po(λ):eλ(t-1)\text{B}(n, p): (q + pt)^{n}, \qquad \text{Po}(λ): e^{λ(t - 1)}IN THE FORMULAE BOOKLETConditionsB(n, p) with q = 1 − p; Po(λ) with λ > 0.
Geo(p):pt1-qt,Neg B(r,p):(pt1-qt)r\text{Geo}(p): \frac{pt}{1 - qt}, \qquad \text{Neg B}(r, p): (\frac{pt}{1 - qt})^{r}IN THE FORMULAE BOOKLETConditionsq = 1 − p, and |qt| < 1 for the series to converge.

Every formula in the library is indexed by unit on the equation index, and the Further Statistics 1 notes are where these results are derived and used. The 3 the booklet does not print are on the list of every formula to memorise, alongside the rest of the course.

Also: Further Pure 1 formulae · Further Pure 2 formulae