Funding for this research was provided by:
Central Research Grant & Direct Allocation, The Hong Kong Polytechnic University (A-PJ86)
Received: 20 April 2018
Accepted: 20 August 2019
First Online: 2 September 2019
Ethics approval and consent to participate
: All of the procedures performed in this study were in accordance with the ethical standard of the 1964 Helsinki declaration and its later amendments. This study was approved by the Human Subjects Ethics Committee of the Hong Kong Polytechnic University (HSAERS20110407005). Written, informed consent was obtained from all of the participants before the commencement of data collection. For participants younger than 18, written passive consent was obtained from their parents or next of kin on their behalf. Written assent was also obtained from the adolescent participants. The ethics committee of the Hong Kong Polytechnic University specifically approved this consent procedure.
: Not applicable.
: The authors declare that they have no competing interests.