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This article provides an overview of the recent literature on the design of blocked and split‐plot experiments with quantitative experimental variables. A detailed literature study introduces the ongoing debate between an optimal design approach to constructing blocked and split‐plot designs and approaches where the equivalence of ordinary least squares and generalized least squares estimates are envisaged. Examples where the competing design strategies lead to totally different designs are given, as well as examples in which the optimal experimental designs are orthogonally blocked or equivalent‐estimation split‐plot designs.

AbstractFertility decline in human history is a complex enigma. Different triggers have been proposed, among others the increased demand for human capital resulting in parents making a quantity–quality (QQ) trade-off. This is the first study that examines the existence of a QQ trade-off and the possible gender bias by analyzing fertility intentions rather than fertility outcomes. We rely on the unified growth theory to understand the QQ trade-off conceptually and a discrete choice experiment conducted among 426 respondents in Ethiopia to analyze fertility intentions empirically. We confirm the existence of a QQ trade-off only when the number of children is less than six and find that intentions are gendered in two ways: (i) boys are preferred over girls, and (ii) men are willing to trade-off more education in return for more children. Results imply that a focus on both stimulating intentions for education, especially girls' education, and on family size intentions is important to accelerate the demographic transition.