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1.
Asymptotic expansions are given for the density function of the normalized latent roots of S1S2?1 for large n under the assumption of Ω = O(n), where S1 and S2 are independent noncentral and central Wishart matrices having the Wp(b, Σ; Ω) and Wp(n, Σ) distributions, respectively. The expansions are obtained by using a perturbation method. Asymptotic expansions are also obtained for the density function of the normalized canonical correlations when some of the population canonical correlations are zero.  相似文献   

2.
Let Sp×p ~ Wishart (Σ, k), Σ unknown, k > p + 1. Minimax estimators of Σ?1 are given for L1, an Empirical Bayes loss function; and L2, a standard loss function (RiE(LiΣ), i = 1, 2). The estimators are Σ??1 = aS?1 + br(S)Ip×p, a, b ≥ 0, r(·) a functional on Rp(p+2)2. Stein, Efron, and Morris studied the special cases Σa?1 = aS?1 (EΣ?k?p?1?1 = Σ?1) and Σ?1?1 = aS?1 + (b/tr S)I, for certain, a, b. From their work R1?1, Σ?1?1; S) ≤ R1?1, Σ?a?1; S) (?Σ), a = k ? p ? 1, b = p2 + p ? 2; whereas, we prove R2?1Σ?a?1; S) ≤ R2?1, Σ?1?1; S) (?Σ). The reversal is surprising because L1?1, Σ?1?1; S) → L2?1, Σ?1?1; S) a.e. (for a particular L2). Assume R (compact) ? S, S the set of p × p p.s.d. matrices. A “divergence theorem” on functions Fp×p : RS implies identities for Ri, i = 1, 2. Then, conditions are given for Ri?1, Σ??1; S) ≤ Ri?1, Σ?1?1; S) ≤ Ri?1, Σ?a?1; S) (?Σ), i = 1, 2. Most of our results concern estimators with r(S) = t(U)/tr(S), U = p ∣S1/p/tr(S).  相似文献   

3.
The following estimate of the pth derivative of a probability density function is examined: Σk = 0Na?khk(x), where hk is the kth Hermite function and a?k = ((?1)pn)Σi = 1nhk(p)(Xi) is calculated from a sequence X1,…, Xn of independent random variables having the common unknown density. If the density has r derivatives the integrated square error converges to zero in the mean and almost completely as rapidly as O(n?α) and O(n?α log n), respectively, where α = 2(r ? p)(2r + 1). Rates for the uniform convergence both in the mean square and almost complete are also given. For any finite interval they are O(n?β) and O(n2log n), respectively, where β = (2(r ? p) ? 1)(2r + 1).  相似文献   

4.
The probability generating function (pgf) of an n-variate negative binomial distribution is defined to be [β(s1,…,sn)]?k where β is a polynomial of degree n being linear in each si and k > 0. This definition gives rise to two characterizations of negative binomial distributions. An n-variate linear exponential distribution with the probability function h(x1,…,xn)exp(Σi=1n θixi)f(θ1,…,θn) is negative binomial if and only if its univariate marginals are negative binomial. Let St, t = 1,…, m, be subsets of {s1,…, sn} with empty ∩t=1mSt. Then an n-variate pgf is of a negative binomial if and only if for all s in St being fixed the function is of the form of the pgf of a negative binomial in other s's and this is true for all t.  相似文献   

5.
Let Σ be an n × n positive definite matrix with eigenvalues λ1λ2 ≥ … ≥ λn > 0 and let M = {x, y | x?Rn, y?Rn, x ≠ 0, y ≠ 0, xy = 0}. Then for x, y in M, we have that x′Σy(x′Σxy′Σy)121 ? λn)1 + λn) and the inequality is sharp. If
∑=11122122
is a partitioning of Σ, let θ1 be the largest canonical correlation coefficient. The above result yields θ11 ? λn)1 + λn).  相似文献   

6.
Let X1, X2, X3, … be i.i.d. r.v. with E|X1| < ∞, E X1 = μ. Given a realization X = (X1,X2,…) and integers n and m, construct Yn,i, i = 1, 2, …, m as i.i.d. r.v. with conditional distribution P1(Yn,i = Xj) = 1n for 1 ? j ? n. (P1 denotes conditional distribution given X). Conditions relating the growth rate of m with n and the moments of X1 are given to ensure the almost sure convergence of (1mmi=1 Yn,i toμ. This equation is of some relevance in the theory of Bootstrap as developed by Efron (1979) and Bickel and Freedman (1981).  相似文献   

7.
Let α(n1, n2) be the probability of classifying an observation from population Π1 into population Π2 using Fisher's linear discriminant function based on samples of size n1 and n2. A standard estimator of α, denoted by T1, is the proportion of observations in the first sample misclassified by the discriminant function. A modification of T1, denoted by T2, is obtained by eliminating the observation being classified from the calculation of the discriminant function. The UMVU estimators, T11 and T21, of ET1 = τ1(n1, n2) and ET2 = τ2(n1, n2) = α(n1 ? 1, n2) are derived for the case when the populations have multivariate normal distributions with common dispersion matrix. It is shown that T11 and T21 are nonincreasing functions of D2, the Mahalanobis sample distance. This result is used to derive the sampling distributions and moments of T11 and T21. It is also shown that α is a decreasing function of Δ2 = (μ1 ? μ2)′Σ?11 ? μ2). Hence, by truncating T11 and T21 (or any estimator) at the value of α for Σ = 0, new estimators are obtained which, for all samples, are as close or closer to α.  相似文献   

8.
Let Lu be the integral operator defined by (Lk?)(x, y) = ∝ s ∝ ?(x′, y′)(eik??) dx′ dy′, (x, y) ? S where S is the interior of a smooth, closed Jordan curve in the plane, k is a complex number with Re k ? 0, Im k ? 0, and ?2 = (x ?x′)2 + (y ? y′)2. We define q(x, y) = [dist((x, y), ?S)]12, (x, y) ? S; L2(q, S) = {? : ∝ s ∝ ¦ ?(x, y)¦2 q(x, y) dx dy < ∞}; W21(q, S) = {? : ? ? L2(q, S), ???x, ?f?y ? L2(q, S)}, where in the definition of W21(q, S) the derivatives are taken in the sense of distributions. We prove that Lk is a continuous 1-l mapping of L2(q, S) onto W21(q, S).  相似文献   

9.
Let {Xn}n≥1 be a sequence of independent and identically distributed random variables. For each integer n ≥ 1 and positive constants r, t, and ?, let Sn = Σj=1nXj and E{N(r, t, ?)} = Σn=1 nr?2P{|Sn| > ?nrt}. In this paper, we prove that (1) lim?→0+?α(r?1)E{N(r, t, ?)} = K(r, t) if E(X1) = 0, Var(X1) = 1, and E(| X1 |t) < ∞, where 2 ≤ t < 2r ≤ 2t, K(r, t) = {2α(r?1)2Γ((1 + α(r ? 1))2)}{(r ? 1) Γ(12)}, and α = 2t(2r ? t); (2) lim?→0+G(t, ?)H(t, ?) = 0 if 2 < t < 4, E(X1) = 0, Var(X1) > 0, and E(|X1|t) < ∞, where G(t, ?) = E{N(t, t, ?)} = Σn=1nt?2P{| Sn | > ?n} → ∞ as ? → 0+ and H(t, ?) = E{N(t, t, ?)} = Σn=1 nt?2P{| Sn | > ?n2t} → ∞ as ? → 0+, i.e., H(t, ?) goes to infinity much faster than G(t, ?) as ? → 0+ if 2 < t < 4, E(X1) = 0, Var(X1) > 0, and E(| X1 |t) < ∞. Our results provide us with a much better and deeper understanding of the tail probability of a distribution.  相似文献   

10.
Let (W4,?W4) be a 4-manifold. Let f1,f2,…,fk:(D2,?D2)→ (W4,?W4) be transverse immersions that have spherical duals α12,…,αk:S2W?. Then there are open disjoint subsets V1, V2,…,Vk of W, such that for each 1?i?k, (a) ?Vi=V1?W and ?Vi is an open regular neighborhood of fi(?D2) in ?W, and (b) (Vi,?Vi,fi(?D2)) is proper homotopy equivalent to (M, ?M, d)—a standard object in which d bounds an embedded flat disk. If we could get a homeomorphism instead of a proper homotopy equivalence, then we would be able to prove a 5-dimensional s-cobordism theorem.  相似文献   

11.
Let X1, …, Xp have p.d.f. g(x12 + … + xp2). It is shown that (a) X1, …, Xp are positively lower orthant dependent or positively upper orthant dependent if, and only if, X1,…, Xp are i.i.d. N(0, σ2); and (b) the p.d.f. of |X1|,…, |Xp| is TP2 in pairs if, and only if, In g(u) is convex. Let X1, X2 have p.d.f. f(x1, x2) = |Σ|?12 g((x1, x2) Σ?1(x1, x2)′). Necessary and sufficient conditions are given for f(x1, x2) to be TP2 for fixed correlation ?. It is shown that if f is TP2 for all ? >0. then (X1, X2)′ ~ N(0, Σ). Related positive dependence results and applications are also considered.  相似文献   

12.
The generalized binomial coefficients (κλ) are defined by
Cλ(Im + R)Cλ(Im) = Σk=0lΣκ(λκ)Cκ(R)Cκ(Im)
, where the Ck(R) are the zonal polynomials of the m × m matrix R. In this paper some simple expressions are derived which allow straightforward calculation of a large number of these coefficients.  相似文献   

13.
Let Σ be a set of n points in the plane. The minimal network for Σ is the tree of shortest total length LM(Σ) whose vertices are exactly the points of S. The Steiner minimal network for Σ is the tree of shortest possible total length LS(Σ) when the vertices are allowed to be any set Σ′ ? Σ. Clearly LS(Σ) ? LM(Σ), since the minimization in LS is over a larger set. It has long been conjectured that, conversely, LS(Σ) ? (3122) LM(Σ), but this has previously been proved only if n = 3. In this paper, among other results, this is proved for n = 4. Unfortunately the proof is sufficiently complicated that immediate generalization to arbitrary n, no matter how desirable, is unlikely.  相似文献   

14.
Let X1,X2,… be independent random variables, and set Wn = max(0,Wn-1 + Xn), W0 = 0, n ? 1. The so-called cusum (cumulative sum) procedure uses the first passage time T(h) = inf{n ? 1: Wn?h}for detecting changes in the mean μ of the process. It is shown that limh→∞ μET(h)/h = 1 if μ > 0. Also, a cusum procedure for detecting changes in the normal mean is derived when the variance is unknown. An asymptotic approximation to the average run length is given.  相似文献   

15.
The Fréchet distance between two multivariate normal distributions having means μX, μY and covariance matrices ΣX, ΣY is shown to be given by d2 = |μX ? μY|2 + trX + ΣY ? 2(ΣXΣY)12). The quantity d0 given by d02 = trX + ΣY ? 2(ΣXΣY)12) is a natural metric on the space of real covariance matrices of given order.  相似文献   

16.
Asymptotic expansions for a class of functional limit theorems are investigated. It is shown that the expansions in this class fit into a common scheme, defined by a sequence of functions hn (ε1,…, εn), n ≥ 1, of “weights” (for n observations), which are smooth, symmetric, compatible and have vanishing first derivatives at zero. Then hn(n?12,…, n?12) admits an asymptotic expansion in powers of n?12. Applications to quadratic von Mises functionals, the C.L.T. in Banach spaces, and the invariance principle are discussed.  相似文献   

17.
It is shown, for n ? m ? 1, that there exist inner maps Φ: BnBm with boundary values Φ1: Bn → Bm such that σm(A) = σn1?1(A)). where σn and σm are the Haar measures on ?Bn and ?Bm, respectively, and A ? Bn is an arbitrary Borel set.  相似文献   

18.
Let V denote a finite dimensional vector space over a field K of characteristic 0, let Tn(V) denote the vector space whose elements are the K-valued n-linear functions on V, and let Sn(V) denote the subspace of Tn(V) whose members are the fully symmetric members of Tn(V). If Ln denotes the symmetric group on {1,2,…,n} then we define the projection PL : Tn(V) → Sn(V) by the formula (n!)?1Σσ ? Ln Pσ, where Pσ : Tn(V) → Tn(V) is defined so that Pσ(A)(y1,y2,…,yn = A(yσ(1),yσ(2),…,yσ(n)) for each A?Tn(V) and yi?V, 1 ? i ? n. If xi ? V1, 1 ? i ? n, then x1?x2? … ?xn denotes the member of Tn(V) such that (x1?x2· ? ? ?xn)(y1,y2,…,yn) = Пni=1xi(yi) for each y1 ,2,…,yn in V, and x1·x2xn denotes PL(x1?x2? … ?xn). If B? Sn(V) and there exists x i ? V1, 1 ? i ? n, such that B = x1·x2xn, then B is said to be decomposable. We present two sets of necessary and sufficient conditions for a member B of Sn(V) to be decomposable. One of these sets is valid for an arbitrary field of characteristic zero, while the other requires that K = R or C.  相似文献   

19.
In “The Slimmest Geometric Lattices” (Trans. Amer. Math. Soc.). Dowling and Wilson showed that if G is a combinatorial geometry of rank r(G) = n, and if X(G) = Σμ(0, x)λr ? r(x) = Σ (?1)r ? kWkλk is the characteristic polynomial of G, then
wk?rk+nr?1k
Thus γ(G) ? 2r ? 1 (n+2), where γ(G) = Σwk. In this paper we sharpen these lower bounds for connected geometries: If G is connected, r(G) ? 3, and n(G) ? 2 ((r, n) ≠ (4,3)), then
wi?ri + nri+1 for i>1; w1?r+nr2 ? 1;
|μ| ? (r? 1)n; and γ ? (2r ? 1 ? 1)(2n + 2). These bounds are all achieved for the parallel connection of an r-point circuit and an (n + 1)point line. If G is any series-parallel network, r(G) = r(G?) = 4, and n(G) = n(G?) = 3 then (w1(G))4t-G ? (w1(G?)) = (8, 20, 18, 7, 1). Further, if β is the Crapo invariant,
β(G)=dX(G)(1),
then β(G) ? max(1, n ? r + 2). This lower bound is achieved by the parallel connection of a line and a maximal size series-parallel network.  相似文献   

20.
Optimization problems are connected with maximization of three functions, namely, geometric mean, arithmetic mean and harmonic mean of the eigenvalues of (XΣX)?1ΣY(YΣY)?1YΣX, where Σ is positive definite, X and Y are p × r and p × s matrices of ranks r and s (≥r), respectively, and XY = 0. Some interpretations of these functions are given. It is shown that the maximum values of these functions are obtained at the same point given by X = (h1 + ?1hp, …, hr + ?rhp?r+1) and Y = (h1 ? ?1hp, …, hr ? ?rhp?r+1, Yr+1, …, Ys), where h1, …, hp are the eigenvectors of Σ corresponding to the eigenvalues λ1 ≥ λ2 ≥ … ≥ λp > 0, ?j = +1 or ?1 for j = 1,2,…, r and Yr+1, …, Ys, are linear functions of hr+1,…, hp?r. These results are extended to intermediate stationary values. They are utilized in obtaining the inequalities for canonical correlations θ1,…,θr and they are given by expressions (3.8)–(3.10). Further, some new union-intersection test procedures for testing the sphericity hypothesis are given through test statistics (3.11)–(3.13).  相似文献   

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