Sturrock R F
Bull World Health Organ. 1975;52(3):267-72.
A total of 6360 mud samples were obtained, in 62 collections made with an exhaustive sampling device, from banana drains on the West Indian island of St Lucia during fortnightly samplings over a 2(1/2)-year period. Analysis of counts of the snail Biomphalaria glabrata from these samples showed that this species had a contagious distribution. This finding is consistent with other evidence that banana drains form a rigorous habitat for B. glabrata. Its distribution was more contagious than that of Oncomelania quadrasi in certain Philippine habitats and several species of aquatic snail in various African irrigation canals. The exact transformation for normalizing the snail counts for standard statistical techniques was z = x(0.287) but the more convenient cube root transformation is probably adequate. However, if too few snails are collected (15 or fewer per 100 samples) or if the frequency distribution of snail counts is discontinuous, with too many widely separated high frequency counts, neither transformation will be entirely satisfactory.
在两年半的时间里，每两周进行一次采样，使用详尽采样设备从西印度群岛圣卢西亚岛的香蕉排水沟中总共采集了62次样本，获得了6360份泥浆样本。对这些样本中光滑双脐螺的数量分析表明，该物种具有聚集分布。这一发现与其他证据一致，即香蕉排水沟为光滑双脐螺形成了一个严格的栖息地。其分布比菲律宾某些栖息地的拟钉螺以及非洲各种灌溉渠道中的几种水生螺的分布更具聚集性。用于标准化蜗牛数量以进行标准统计技术分析的确切变换是z = x(0.287)，但更方便的立方根变换可能就足够了。然而，如果收集到的蜗牛数量太少（每100个样本中15个或更少），或者蜗牛数量的频率分布不连续，有太多广泛分散的高频计数，那么这两种变换都不会完全令人满意。
