$4\mathrm{.}1$ Identify and describe two appropriate metrics than can be used to measure the overall user experience. $(2$ x $3$ marks$)$

$4\mathrm{.}2$ Based on your answer in question $4\mathrm{.}1,$ when would you collect data to measure the overall user experience as part of your usability study, and what is the advantage of collecting data at these intervals?