7. Validation of Research Instruments
The topics identified under the content area for the study above were used to prepare the table of specification for the
items based on the Bloom’s taxonomy of educational objectives. Fourty objective item or questions were initially
drawn. Majority of the questions were on the application and higher order objectives since the study is based on
students’ ability to solve numerical problems in chemistry. This instrument was then given out to two experienced
Chemistry teachers in the secondary schools and who are seasoned examiners of WAEC and NECO for comments on
how well the items were in measuring the expected knowledge and on the correctness of the questions. Based on the
comments of the assessors few questions that needed slight adjustment were corrected.
The instrument was then field-tested on a random sample of twenty five (25) students drawn from a Senior Secondary
class three in Ife East Local government of Osun State. The result of the field test was used to calculate the difficulty
index (p) of the test items. Those items with p value between 0.32 and 0.72 were selected. Based on this, fifteen test
items were dropped and twenty five items retained. The final set of twenty – five questions was the PSATC. The
reliability of the instrument was also determined using the Kuder Richardson formula 21 (K-R 21) and the reliability
coefficient was found to be 0.92