Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Question content and options for the explanatory variable and objective variable.
| Explanatory Variable | Contents of Question |
|---|---|
| Type of lessons | What type of lesson you are attending? |
| 1. sports club; 2. cultural school; 3. cram school; 4. other; 5. no lessons | |
| Objective Variable | |
| Glasses | Do you wear glasses? |
| 1. yes; 2. no |
