How to calculate MOS_zscore in koniq10k datasets?

[lijun-chiebot]

such as c1 = 0, c2 = 0, c3 = 25, c4 = 73, c5 = 7, c_total = 105, MOS = 3.83, SD = 0.53

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The ACR scores are first normalized for each user by z-scoring the user ratings.

[jianyesysu]

The ACR scores are first normalized for each user by z-scoring the user ratings.

What does 'c1,c2,c3,c4,c5,c_total,SD' mean?

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c1 to c5 are the number (counts) of the rating for each of the 5 scale values, from bad (1) to excellent (5). c_total is the total number of ratings a stimulus obtained. SD is the standard deviation of those ratings.