In terms of number of respondents required for utility data, is there any standardized formula to calculate? And whether it is justifiable to calculate using proportion estimation? In case of the limited sample (e.g. rare disease, low survival rate) and do not meet the expected sample (as calculated) that may cause wide standard error and affect QALY, could the sample still be used for the analysis? In this case, adding the number of samples would be extremely difficult. If we borrowed utility from other studies (other countries), any adjustment to be considered? and how to measure the transferability? Many thanks.