X mean value of valence (Y , mean value of arousal) N total number of emotional words within the message φi,t topic distribution for word i in the t th topic µ word's mean value of valence (equivalently for arousal) σ word's standard deviation of valence (equivalently for arousal) (2) calculates the sentiment score of a message by estimating the overall mean value of all emotional words within the message (see Table 2).
x (respectively, Y ) is the overall mean value of the valence (respectively, arousal) considering the N emotional words within the message.