The 1 st Cumulant or moment (a 1) is used to calculate the intensity weighted Z average mean size and the 2 nd moment (a 2) is used to calculate a parameter defined as the polydispersity index (PdI). It is important to note here, that the Cumulants analysis algorithm does not yield a distribution â it gives only the intensity weighted Z average and the polydispersity index.
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For example, it is not right to say simply that a new grade 4 will equal a current grade C. The read across is at the bottom of each grade, so that broadly the same proportion of students will get 4 and above as currently get C and above.A subtle but important difference.ew GCSEs in English language, English literature and maths will be taught in schools in England from September 2015, with students getting their results in August 2017. The new GCSEs will be graded 1 to 9, with 9 being the top grade.