Blue-footed Boobies from the Galapagos

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FALL 2011 - SEYS 562

SEYS 562 Home

Queens College/CUNY
Education Unit
Fall 2011

Item Difficulty - the percentage of pupils who got the item right

Item Difficulty = R/T x 100

R=the number of pupils who got the item right

T= total number of pupils who attempted the item

Item Discriminating Power is the degree to which the item discriminates between pupils with high achievement and low achievement

Item Discriminating Power = R u - R L
.................................................. 1/2T

R L = the number of pupils in the lower group (lower ten scores) who got the item right (you can also use percentages)

R U = the number of pupils in the upper group ( upper ten scores) who got the item right (you can also use percentages)

T = the total number of pupils who attempted the item