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The ratios of their standard deviations to their corresponding mean values in the standard test samples could probably be used as an indicator of porosity , i.e .
 process characterization: standard deviations; concept or principle: standard; concept or principle: samples; material: be; material: as; machanical property: porosity
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: manufacturing standard, machanical property, manufacturing process, material, engineering feature, process parameter, machine or equipment, application, process characterization, enabling technology, biomedical, concept or principle 
Text: {0} 
 Entities: standard deviations, standard, samples, be, as, porosity 
Answer:
 process characterization: standard deviations; concept or principle: standard; concept or principle: samples; material: be; material: as; machanical property: porosity