Sage advice. Experienced physician executives share the secrets of their success. Interview by David O. Weber

Seven successful physician executives, now retired from distinguished careers, look back over their experiences and offer advice for those who follow. Be a good doctor first, and never let business interests undermine the ethics of the health care profession. Prepare for management responsibilities with business training. Seek out mentors and develop a network of knowledgeable colleagues and advisors. Exert leadership rather than authority. Expect disappointments and arm yourself for them.     

Screening for Chlamydia trachomatis in college women on routine gynecological exams.

Chlamydia trachomatis infection poses a serious threat to sexually active college women. Past research has demonstrated the difficulty of predicting infection on the basis of symptoms or physical exam. Recent studies highlight the prevalence of asymptomatic chlamydia infections. This study presents the results of screening 2,303 women for chlamydia infection on routine annual gynecological examinations at a college health center during a 22-month period. A prevalence of 6% was found. The study also assessed the differences between the 140 women identified as chlamydia positive and a control sample of 140 women who were chlamydia negative. The authors compared groups for signs and symptoms that might predict infection, but found no useful predictors. In fact, 79% of the patients who tested positive had no symptoms, and 58% of these had no signs, symptoms, or concurrent infections. Routine screening of women on annual gynecological exam is necessary to bring the chlamydia epidemic under control, the authors conclude.     

Evaluation of Camp Tortuga, a two week children's therapeutic day camp via goal attainment scaling and locus of control

The present study evaluated the effectiveness of a two-week therapeutic day camping experience in facilitating change in children aged 8–12 years with adjustment or behavioral problems. For each of the 42 children attending camp, three Goal Attainment Scales (GAS) were administered before camp separately to the children, parents and counselors. These scales specified individualized behavioral goals for problem areas relating to self, family, children, and group which could be realistically attainable within two weeks. Post-camp GAS follow-up showed that children, parent, and counselor groups each perceived the children as achieving significant positive change in regard to specified goals. Children were also administered a locus of control measure. The hypothesis that “internals” would be perceived as achieving significantly more positive behavioral change on the GAS than “externals” was confirmed. Discussion centered on the viability of therapeutic camping, the merits of using the GAS and the multi-informant approach, and specific therapeutic strategies indicated by the present findings.     

The impact of opening markets on Mexican male/female wage and occupational differentials

This article addresses the effect of a more open market under NAFTA on the economic status of Mexican women. It is assumed that increases in export processing and tourism, industries that have a high demand for female labor, will result from the agreement. The approach of this study is to use regression and correlation analysis to compare wage and occupational differences in two Mexican cities: Tijuana, on the U.S.-Mexican border, and Torreon, in the interior. A major findings is that the overall wage gap is statistically significantly lower where there is increased export processing activity, but there appears to be very little change in occupational segregation. Three additional impacts are: first, that labor force participation rates increase for both men and women, but proportionally more for women. Second, the higher labor demand appears to weaken the relationship between the job qualifications of education and experience and wages. Third, wages by gender are more equal, but for the labor force as a whole there is a greater level of wage dispersion.     

A note on reflecting boundaries for solutions of stochastic differential equations

In this note, sufficient conditions are given for a function g(t) to be a reflecting barrier for the sample paths of a solution process X(t) of a stochastic differential equation.     

Book reviews

Qualitative Sociology -     

ALL THE GAUSSIAN WHITE NOISE SERIAL COVARIANCE MOMENTS TO ORDER FOUR

Using a recursive method, we obtain all the cumulants, central moments, and moments about zero, up to order 4, for the mean-corrected serial covariances from series realisations of length n, given a Gaussian white noise process. Some implicit higher order results are also derived.     

Child deaths attributed to abuse and neglect: An empirical study

This study of 267 child deaths associated with abuse or neglect in Texas during 1975 through 1977 suggests a number of indicators for identifying potential child fatalities. Families where abuse or neglect is implicated in a child fatality are characterized by small family size, young parents, and under-utilization of community support services. Over three-fourths of the families in the study had never come to the attention of the state's child protective services agency. In addition, when fathers were present in the home, they were as likely to be involved in the abuse or neglect as mothers. Neglect was implicated in the death of a child as often as abuse. The study suggests the need for further examination of child fatality profiles associated with abuse and neglect and increased community outreach efforts to provide support to high-risk families, The study also has implications for social policy decisions, particularly in relation to efforts to resist attempts to exclude neglect from child protective service responsibility.     

Theory of factorial designs of the parallel flats type. I: the coefficient matrix

Let GF(s) be the finite field with s elements.(Thus, when s=3, the elements of GF(s) are 0, 1 and 2.)Let A(r×n), of rank r, and c_i(i=1,…,f), (r×1), be matrices over GF(s). (Thus, for n=4, r=2, f=2, we could have A=[¹¹¹⁰₀₁₂₁], c₁=[¹₀], c₂=[⁰₂].) Let T_i (i=1,…,f) be the flat in EG(n, s) consisting of the set of all the s^n?r solutions of the equations At=c_i, wheret′=(t₁,…,t_n) is a vector of variables.(Thus, EG(4, 3) consists of the 3⁴=81 points of the form (t₁,t₂,t₃,t₄), where t's take the values 0,1,2 (in GF(3)). The number of solutions of the equations At=c_i is s^n?r, where r=Rank(A), and the set of such solutions is said to form an (n?r)-flat, i.e. a flat of (n?r) dimensions. In our example, both T₁ and T₂ are 2-flats consisting of 3^4?2=9 points each. The flats T₁,T₂,…,T_f are said to be parallel since, clearly, no two of them can have a common point. In the example, the points of T₁ are (1000), (0011), (2022), (0102), (2110), (1121), (2201), (1212) and (0220). Also, T₂ consists of (0002), (2010), (1021), (2101), (1112), (0120), (1200), (0211) and (2222).) Let T be the fractional design for a sⁿ symmetric factorial experiment obtained by taking T₁,T₂,…,T_f together. (Thus, in the example, 3⁴=81 treatments of the 3⁴ factorial experiment correspond one-one with the points of EG(4,3), and T will be the design (i.e. a subset of the 81 treatments) consisting of the 18 points of T₁ and T₂ enumerated above.)In this paper, we lay the foundation of the general theory of such ‘parallel’ types of designs. We define certain functions of A called the alias component matrices, and use these to partition the coefficient matrix X (n×v), occuring in the corresponding linear model, into components X._j(j=0,1,…,g), such that the information matrix X is the direct sum of the X′._jX._j. Here, v is the total number of parameters, which consist of (possibly μ), and a (general) set of (geometric) factorial effects (each carrying (s?1) degrees of freedom as usual). For j≠0, we show that the spectrum of X′._jX._j does not change if we change (in a certain important way) the usual definition of the effects. Assuming that such change has been adopted, we consider the partition of the X._j into the X_ij (i=1,…,f). Furthermore, the X_ij are in turn partitioned into smaller matrices (which we shall here call the) X_ijh. We show that each X_ijh can be factored into a product of 3 matrices J, ζ (not depending on i,j, and h) and Q(j,h,i)where both the Kronecker and ordinary product are used. We introduce a ring R using the additive groups of the rational field and GF(s), and show that the Q(j,h,i) belong to a ring isomorphic to R. When s is a prime number, we show that R is the cyclotomic field. Finally, we show that the study of the X._j and X′._jX._j can be done in a much simpler manner, in terms of certain relatively small sized matrices over R.     

A note on the asymptotic generalised variance for a moving average process

Relationships between the asymptotic generalised variance, of an r^th order moving average process, and the ordinary variance, of an associated r^th order autoregressive process, are established for r=1 and 2. This is extended to the case r=3, and a generalisation is suggested for all r>O, though this has not been checked beyond r=4.