The item standard deviation is the square root of the average squared deviation of the scores in one item from the item mean.
The standard deviation of the total mean is the square root of the average squared deviation of all total scores from the total mean score.
The adjusted total standard deviation is the standard deviation of the total score after omitting an item.
|xi||the ith observation|
|mean of the observations|
|N||number of nonmissing observations|