Lab report Example | Topics and Well Written Essays - 1500 words

Lab Report Example Quiz I: Psychometric Analysis The 12 item quiz described as Quiz I was associated with a mean of 6.4 and an SD of 2.657 (min = 0, max = 12). The distribution of the total scores was not very normal with skew observed to be 0.111 and kurtosis to be -0.888. The Pearson correlations between the 12 items in the quiz are reported in table 1. This shows that while the test has otherwise acceptable psychometric properties, some items may need to be revised or removed. An item discrimination analysis was conducted to investigate the contribution of each item to the test. Specifically, D index values were estimated for each of the 12 items in the quiz based on splitting the sample into high (73rd percentile and above) and low (27th percentile and below) quiz performers in accordance with Kelly (1939). Based on a frequency table analysis of the ‘quiz I performance’ variable, the split corresponded to scores of 4 or lower being associated with the lower set while scores of 9 or hig her were associated with the higher set. Table 2 shows discriminatory index for each of the items, and it is evident that items 11 and 12 did not achieve a D index of more than 29%. This could mean that these items are poorly constructed or that they do not contribute to the test as well as the other items (Crocker & Algnia, 1986). The item total correlations also verify that these items contribute poorly to the quiz and have correlation coefficient s of less than 0.20. The internal consistency analysis conducted using the Cronbach’s ? was also marginally below the requisite 0.70 level (Nunnally & Brenstien, 1994) with a statistic value of 0.683. Given this data, it was believed that the quiz needed to be revised. Thus, items 12 and 11 were sequentially removed from the quiz and the Cronbach’s ? was re-estimated. The quiz was now composed of 10 items and was associated with an acceptable ? level of 0.734. The revised scale had a mean score of 5.128 with SD = 2.56 (min = 0, max = 10).the distribution of scores for the new quiz was also slightly more normalized with skew = 0.20 and kurtosis = -0.780. Quiz II: Psychometric analysis The 11 item quiz described as Quiz II was associated with a mean of 5.48 and an SD of 2.67 (min = 0, max = 11). The distribution of the total scores was approximately normal with skew observed to be 0.043 and kurtosis to be -0.8. The Pearson correlations between the 11 items in the quiz are reported in table 3. This shows that the test has acceptable psychometric properties. An item discrimination analysis was conducted to investigate the contribution of each item to the test. Specifically, D index values were estimated for each of the 11 items in the quiz based on splitting the sample into high (73rd percentile and above) and low (27th percentile and below) quiz performers in accordance with Kelly (1939). Based on a frequency table analysis of the quiz performance variable, the split corresponded to scores of 4 or lower being associated with the lower set while scores of 7 or higher were associated with the higher set. Table 4 shows discriminatory index for each of the items, all of which managed to achieve an acceptable D index (Crocker & Algnia, 1986). The item total correlations also verify that all items did contribute adequately to the quiz and