STATISTICS IN THE NEW MILLENNIUM: SOME PERSONAL VIEWS

In this paper I discuss three topics that I believe are relevant to the subject of statistics in the new millennium: (a) the impact of computers, and the state of computer-intensive methods as far as practical applications of statistics are concerned; (b) methods for the analysis of the extremely large data sets that are now becoming available; and (c) the use of statistics by scientists in general. For the first topic I suggest that the main advantage of computer-intensive methods is that they can under certain circumstances give simple and believable answers to questions when other methods fail. However, I caution against the uncritical use of computer power without proper checks that analyses work, particularly when conclusions are dependent on very complicated models with many assumptions that are difficult or impossible to verify. For the second topic I note that statistics grew up as a means of extracting the maximum amount of information from small sets of data, and we are now having some difficulty in adapting methods to huge data sets because sometimes the analyses that we might want to do are not possible even with today\u27s powerful computers. I discuss this particularly in terms of the analysis of resource selection data by animals where geographical information system data are available to describe what is available for animals to use. For the third topic I suggest that statistics and statisticians have something of an \u27image\u27 problem with scientists in general. Many scientists do not appear to regard statistics as important for their discipline, and yet errors in the analysis and interpretation of data seem to be fairly common in the scientific literature

Measurement of the Charged Multiplicities in b, c and Light Quark Events from Z0 Decays

Average charged multiplicities have been measured separately in $b$, $c$ and light quark ($u,d,s$) events from $Z^0$ decays measured in the SLD experiment. Impact parameters of charged tracks were used to select enriched samples of $b$ and light quark events, and reconstructed charmed mesons were used to select $c$ quark events. We measured the charged multiplicities: $\bar{n}_{uds} = 20.21 \pm 0.10 (\rm{stat.})\pm 0.22(\rm{syst.})$, $\bar{n}_{c} = 21.28 \pm 0.46(\rm{stat.}) ^{+0.41}_{-0.36}(\rm{syst.})$ $\bar{n}_{b} = 23.14 \pm 0.10(\rm{stat.}) ^{+0.38}_{-0.37}(\rm{syst.})$, from which we derived the differences between the total average charged multiplicities of $c$ or $b$ quark events and light quark events: $\Delta \bar{n}_c = 1.07 \pm 0.47(\rm{stat.})^{+0.36}_{-0.30}(\rm{syst.})$ and $\Delta \bar{n}_b = 2.93 \pm 0.14(\rm{stat.})^{+0.30}_{-0.29}(\rm{syst.})$. We compared these measurements with those at lower center-of-mass energies and with perturbative QCD predictions. These combined results are in agreement with the QCD expectations and disfavor the hypothesis of flavor-independent fragmentation.Comment: 19 pages LaTex, 4 EPS figures, to appear in Physics Letters

Statistika untuk ilmu dan manajemen lingkungan

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Life histories of an invasive and native ladybird under field experimental conditions in a temperate climate

Among characteristics that are thought to determine the success of invasive species, life-history traits feature prominently. However, in most cases, these have been determined under laboratory conditions. Here, we use a field set-up to determine immature development time and survival of invasive Harmonia axyridis (Pallas) and native Adalia bipunctata L. (both Coleoptera: Coccinellidae). On caged Tilia × europaea L. cv. Pallida trees (Malvaceae) with ample amounts of aphid food, we introduced freshly hatched larvae of a single or of both ladybird species and followed their development until emergence of adults. Under the condition of ample prey availability, both ladybird species apparently hardly interacted and intraguild predation did not cause significant mortality. Development time of both species is in line with data from laboratory tests under controlled conditions. Immature survival can reach high levels, but is considerably higher for H. axyridis (44-100%) than for A. bipunctata (11-77%), resulting in faster increase of H. axyridis populations, which is one of the factors that may explain its invasion success