The 7352 questionnaires in the CLHLS dataset, clustered by the number of unanswered questions and the partial score obtained on the answered questions. Top right corner: the questionnaires space, where subjects that are examined by a MMSE questionnaire are represented as points whose coordinates are the maximum score that can be obtained on the unanswered items of the questionnaire and the partial score that has been obtained on the answered items, in an example when the maximum total score that can be obtained is equal to J. If the MMSE index grades the total score according to a cut-off d, subjects in the lower (upper) triangle receive an index level 0 (1), while the index level is missing for all the questionnaires that are included in the parallelogram.