Defective data in the analysis of variance

Several kinds of defective data are considered, the first being that of data completely missing. General expressions for block designs are given for the variances of treatment contrasts. Sometimes even a moderate loss of data will seriously increase an important variance. A similar defect arises when some plots receive the wrong treatment. Again the consequences can be serious though, if the correct form of analysis used, variances of contrasts may be much better estimated than if defective data are regarded as missing. Finally, the problem of the mixed-up plots is considered, the total value for certain plots being known but not the individual data. Formulae are presented for dealing with such a case. Again the correct form of analysis can sometimes retain useful information that would be lost if affected plots are regarded as missing. Finally some considerations are set out for dealing with defective data in general.