Table 4.

Intercoder agreement for our labeled datasets (Krippendorff alpha).

Category	WebMD	TwitterHealth	Google+Health
Share experiences	0.349	0.446	0.109
Ask for specific medical advice or information	0.768	0.225	0.108
Request or give psychological support	0.219	0.090	−0.007
About family (not about self)	0.736	0.322	−0.010
Share news	N/Aa	0.083	0.083
Jokes	N/A	0.177	0.029
Advertisement	N/A	0.220	0.107
Personal opinion	N/A	0.103	0.038
Educational material	N/A	0.164	0.091

^aN/A: not applicable.