( 750) () (n) ( 80) ?

13. - =3 36 ' =1,5. 0,05 , =1 >1.

1, 1,65 - 1, 1,65 - 1, 1,96 - 1,65, 1,5 - 1,5, 1,96 -

2- . 3- .

2- . 3- .

2- . 3- .

Sample size:1PL = 100 minimum2PL = 300 minimum3PL = 500 minimumThe a parameter ranges from 0.0 to about 2.0 in practice (theoretically to infinity)Higher means better discriminatingFor achievement testing, 0.7 or 0.8 is goodAptitude testing is a little higherShould be between -3 and 399.9% of students are in that range0.0 is average1.0 is difficult (85th percentile)-1.0 is easy (15th percentile)The c parameter should be about 1/k, where k is the number of optionsIf higher, this indicates that options are not attractive