Tomato Capsule

K - number of items p - proportion of the examinees who got the item right q - proportion of the examinees who got the item wrong σ 2 X -  variance or the square of the standard deviation

WHERE: K - number of items p - proportion of the examinees who got the item right q - proportion of the examinees who got the item wrong σ 2 X - variance or the square of the standard deviation