Teenage suicide in King County, Washington. I. Rates of suicide for 26 years

The population-adjusted rate of teenage suicide in King County, Washington, was reviewed for the 26 years from 1959 to 1984. For the entire period, the rate did not change significantly. An abrupt change did occur during the middle of this period, but, for reasons discussed in the text, this may well represent a change in procedures and philosophy of death certification rather than a real change in rate. Reasons for the apparent discrepancy with national statistics are discussed.     

Duration of the time to reconviction: Evidence from UK prisoner discharge data

Duration models were used to investigate reconviction risks for a sample of 34,126 offenders released from prison in England and Wales during 1998. Different versions of the Cox proportional hazards model were applied to a comprehensive data set covering several offense types. Factors such as age (modelled using bands rather than a linear or quadratic format), gender, convictions-history, and offense type were found to be strongly associated with the risk of reconviction. Interactions between factors were also included and it was shown that the discrepancy between the risk of reconviction for males and females became weaker as the number of previous convictions increased. The study helped identify the subgroups of offenders for whom reconviction risks are greatest and the times when they seem to be most vulnerable to reconviction. Implications are explored for the design of prisoner resettlement programs and the prioritization of offenders for more intensive forms of intervention.     

Spatial variation of refractive index in a pane of float glass.

In the statistical interpretation of forensic glass evidence it is standard practice to make the assumption of homogeneity of the refractive index (RI) of the source glass, or of localized homogeneity. However, the work of Locke and Hayes showed that, for toughened windscreen glass, this assumption might not be true. This work is well cited, but there appears to have been little follow-on published research. Furthermore, the toughening process is something known to affect the refractive index, and is a process that float glass does not undergo. Float glass is a major component of casework in New Zealand and for that reason it would be interesting to know whether the findings of Locke and Hayes apply when dealing with float glass. In this paper we describe an experiment similar to that of Locke and Hayes, systematically examining the variation of RI in a pane of float window glass. It was found that, although there were no systematic differences in refractive index, there were observable differences across the pane.     

A statistical approach to drug sampling: a case study.

In many countries it is left to the discretion of the court to accept or reject conclusions based on sampling procedures as applied to the total drug exhibit. As an alternative to this subjective approach, a statistical basis is presented using binomial and hypergeometric distributions to determine a lower limit for the proportion of units in a population which contains a drug, at a given confidence level. A method for calculating the total weight of a drug present in a population within a given confidence interval is also presented. In the event of no failures (all units sampled contain a drug), a sample size of six or seven units is generally sufficient to state that a proportion of at least 0.70 of the population contains a drug at a confidence level of at least 90%. When failures do occur in the sample, point estimation is used as the basis for selecting the appropriate sample size.