They occur, e.g., due to measurement errors, differences between experimental units and differences in environmental conditions experimental units are exposed to. Observations made in experiments deviate from their expected values. Conclusionīlocking with a fixed-position arrangement was more efficient in improving precision of greenhouse experiments than re-arrangement of pots and hence can be recommended for comparable greenhouse experiments. An α-design with block size four performed best across seven plant growth traits.
All designs with fixed-position arrangement, which accounted for the known north–south gradient in the greenhouse, outperformed re-arrangement. ResultsĪ uniformity greenhouse experiment with barley ( Hordeum vulgare L.) to compare re-arrangement of pots with a range of designs under fixed-position arrangement showed that both methods can reduce the residual variance and the average standard error of a difference. While re-arrangement is commonly done in greenhouse experiments, data to quantify its usefulness is limited. If re-arrangement is successful, the time-invariant positional effect can average out for experimental units moved between different positions during the experiment. This re-arrangement enables a separation of variation due to time-invariant position effects and variation due to the experimental units. pots within a greenhouse) are mobile, they can be re-arranged during the experiment. Using a suitable experimental design, a part of the variance can be captured through blocking of the experimental units. In statistical analysis errors can be modelled as independent effects or as spatially correlated effects with an appropriate variance–covariance structure. These errors can arise from measurement error, local or positional conditions of the experimental units, or from the randomization of experimental units. Observations measured in field and greenhouse experiments always contain errors.
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