RRI Publications

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Subject: search.filters.subject.Statistical analysis

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    An analysis of growth patterns of Hevea clones
    (Rubber Research Institute. Agalawatta, 1988) Margret, H.A.W.; Abeyasekera, S.; Jayasekera, N.E.M.
    Four girth measurements collected over four years, before tapping from ten Hevea clones grown in two sites have been analysed to study the growth pattern. Year to year variation in both sites was mainly due t linear component of growth. Growth of individual clones too was mainly due to linear effect. But some clones in one site showed significant quadratic and or cubic component. This was due to non linear growth of plants in some plots. Ten clones have been groued (a) according to the when averaged over four years so that clones within a group have the same average girth and (b) on the gradient of the regression fitted to the girth measurement increasing over the four years. RRIC 52 had the fastest growth in both sites. RRIC 103 had the same growth rates in both sites suggesting that it has a greater stability to local environmental changes.
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    Impact of production consumption, exports and stocks on the price of natural rubber in Sri Lanka
    (Rubber Research Institute. Agalawatta, 1997) Wijesuriya, B.W.; Thattil, R.O.
    The relationship between price of Natural Rubber (NR)with factors such as:production,consumption,exports and stocks are important in identifying the nature of competetion and therefore reveals the market structure for NR.This paper examines these relationships and also the seasonal variation of these factors,using time series statistical tools,viz Cross Correlation Functions (CCF)and seasonal indices. There is a marked seasonality in production with values below average during April to October (2nd and 3rd quarters).Prices tend to fall when the production rises.A similar phenomenon was observed between price and exports.However,the effect of production or exports on price is mild. A similar pattern of seasonal variation was observed for consumption and stocks of NR.More rubber is consumed during the latter part of the year.An accumulation of stocks was observed towards the end of the year.However,price of NR was not significantly related to consumption or stocks.This is mainly due to the fact that only a few buyers influence prices through their purchase and by adjustments of stocks as in an oligopolistic market.
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    Analysis of ranking exercises in participatory rural appraisal (PRA). a case study from the smallholder rubber sector
    (Rubber Research Institute. Agalawatta, 2005) Wijesuriya, W.; Thattil, R.O.
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    Methods of data analysis for intercropping systems under rubber
    (Rubber Research Institute. Agalawatta, 2001) Wijesuriya, W.; Thattil, R.O.
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    Evaluation of ISO recommendation on analysis of precision experiments for statistical quality control
    (Rubber Research Institute. Agalawatta, 1999) Wijesuriya, W.; Thattil, R.O.
    Application of appropriate statistical methods is an important task in any quality control process as various statistical approaches such as;sampling,experimentationand process control are involved in quality control lprocesses.This has become an essential practice in many areas since the introduction of ISO quality assurance scheme .This article focuses on precision experiments where several laboratories are compared for a standard measurement method.The whole plrocess of analysis and interpretation suggested by ISO is evauated and documented in a sequential order.In addition to the ISO recommendation,additional graphical methods are suggested for better judgement .The statisticans role as a member of the panel is also lpresented at each step of the quality control process.