Optimum Sample Size and Sampling Interval for Controlling the Mean of Non-Normal Variables

Abstract

Following Duncan [3], the per hour cost of the process under the surveillance of a mean chort for controlling the mean of non-normal variables whose density function is represented by the first four terms of an Edgeworth series is obtoined. The sample size and sompling interval which minimize the cost for detecting a particular shift in the process average are derived when the width of the control limits is specified. They are numerically determined for different non-normol situations by assuming various cost valuer when a particular shift in the process averoge is to be detected. They are presented in a fable which compares the changes in optimum sample size and sompling interval due to changes in [ a ) the non-normal sifuotion, (b) the shifts to be detected in the process averoge and (c) width of the control limits specified.

Construction of Control Charts to Help in the Stability and Reliability of Results in an Accredited Water Quality Control Laboratory

“…In the previous and subsequent samples, the results were satisfactory within the control lines, as expected. According to Nagendra and Rai [28], the chart series size, sample size, and sampling interval are the three main factors in detecting changes efficiently. Thus, for further investigation of the cause of this variation, a larger number of samples is required.…”

Princípios básicos de procedimentos estatísticos aplicados na análise de dados de vigilância em saúde pública: uma revisão

“…Considerando que esses dois procedimentos de controle estatístico de qualidade, por sua simplicidade e facilidade de implementação, são adequados para serem adaptados à rotina de análise de dados de vigilância em saúde pública, é conveniente citar que a literatura específica é rica em referências relativas a tais procedimentos, entre as quais: Montgomery (1980), relacionado a questões econômicas; Page (1957), Hinkley (1971), Pettitt (1979Pettitt ( , 1980 e Assaf et al (1992), relacionados ao problema change point; Nagendra & Rai (1971) e Frisén & De Maré (1991, relacionados a questões de otimalidade; Alwan (1986) e Pignatiello Jr. & Runger (1990), a questões de Cusum multivariado; Ncube & Woodall (1984), Westgard et al (1977) e Lucas (1982), para questões relacionadas à combinação de esquema Shewhart -Cusum.…”