One, two, three: portable sample size in agricultural research. (25th December 2022)

• Record Type: Journal Article
• Authors: Piepho, Hans-Peter; Gabriel, Doreen; Hartung, Jens; Büchse, Andreas; Grosse, Meike; Kurz, Sabine; Laidig, Friedrich; Michel, Volker; Proctor, Iain; Sedlmeier, Jan Erik; Toppel, Kathrin; Wittenburg, Dörte
• Is Part Of: Journal of agricultural science. Volume 160:Number 6(2022)
• Page Start: 459
• Page End: 482
• Publication Date: 2022-12-25
• Subjects: Experimental design -- linear model -- power -- precision -- replication; Agriculture -- Periodicals; 630.5
• DOI: 10.1017/S0021859622000466
• Languages: English
• ISSNs: 0021-8596

Abstract

Abstract: Determination of sample size (the number of replications) is a key step in the design of an observational study or randomized experiment. Statistical procedures for this purpose are readily available. Their treatment in textbooks is often somewhat marginal, however, and frequently the focus is on just one particular method of inference (significance test, confidence interval). Here, we provide a unified review of approaches and explain their close interrelationships, emphasizing that all approaches rely on the standard error of the quantity of interest, most often a pairwise difference of two means. The focus is on methods that are easy to compute, even without a computer. Our main recommendation based on standard errors is summarized as what we call the 1-2-3 rule for a difference of two treatment means.