Much of the research in operations management deals with the study of events. These events take many different forms: the length of time until a job is completed, the time interval until a component breaks down or the time taken for the development and introduction of a new product. When studying events, we are often interested in examining how factors such as the introduction of a new dispatching rule or a change in the level of capacity utilization affect the resulting events (e.g., completion time for a job). Analyzing events is not an easy task. Events are often time‐varying (where the probability of the event taking place changes over the life of the event), seldom normally distributed (with the distributions often being highly skewed) and affected by censoring (observations lacking a beginning or ending point). Finally, information about events is frequently collected longitudinally. These traits create problems for the application of such commonly used procedures as ANOVA. To cope with such problems, new statistical tools are needed. This paper introduces such a statistical procedure, survival analysis. Survival analysis is a set of statistical techniques (non‐parametric, semi‐parametric and parametric) used to determine quantitatively the impact of independent variables on a dependent variable which represents the time interval between events. The usefulness of this procedure is illustrated by applying it to data taken from a study focusing on the blood donation process. The paper concludes by pointing out some of the problems encountered in operations management which can be readily analyzed using this procedure. Overall, the paper tries to make the reader aware of the capabilities offered by survival analysis.

DESS is a formulation widely used to preserve DNA in biological tissue samples. Although it contains three ingredients, dimethyl sulfoxide (DMSO), ethylenediaminetetraacetic acid (EDTA) and sodium chloride (NaCl), it is frequently referred to as a DMSO-based preservative. The effectiveness of DESS has been confirmed for a variety of taxa and tissues, however, to our knowledge, the contributions of each component of DESS to DNA preservation have not been evaluated. To address this question, we stored tissues of three aquatic taxa, Mytilus edulis (blue mussel), Faxonius virilis (virile crayfish) and Alitta virens (clam worm) in DESS, each component of DESS individually and solutions containing all combinations of two components of DESS. After storage at room temperature for intervals ranging from one day to six months, we extracted DNA from each tissue and measured the percentage of high molecular weight (HMW) DNA recovered (%R) and normalized HMW DNA yield (nY). Here, HMW DNA is defined as fragments >10 kb. For comparison, we also measured the % R and nY of HMW DNA from extracts of fresh tissues and those stored in 95% EtOH over the same time intervals. We found that in cases where DESS performed most effectively (yielding � 20%R of HMW DNA), all solutions containing EDTA were as or more effective than DESS. Conversely, in cases where DESS performed more poorly, none of the six DESS-variant storage solutions provided better protection of HMW DNA than DESS. Moreover, for all taxa and storage intervals longer than one day, tissues stored in solutions containing DMSO alone, NaCl alone or DMSO and NaCl in combination resulted in %R and nY of HMW DNA significantly lower than those of fresh tissues. These results indicate that for the taxa, solutions and time intervals examined, only EDTA contributed directly to preservation of high molecular weight DNA.

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