Application exercises

A. Examine the data set presented in Table 4.11 and use it to calculate all of the statistics needed to fill in the results in Table 4.12.

TABLE 4.11: SCORES ON PRETEST B

TABLE 4.12: PRETEST RESULTS FOR FORM B

STATISTIC        PRETEST B

N
k
M
S
LOW
HIGH
RANGE

B. Examine the results shown in Table 4.13. Which test has the largest number of students? Which test has the highest central tendency? Which test has the most dispersion? Which test appears to be normally distributed? Which one is negatively skewed? Which one is positively skewed?

TABLE 4.13: IMAGINARY RESULTS FOR THREE FORMS OF A CRT

C. Next, examine Table 4.14. You will note that it is exactly the same as Table 4.8 except that the cut-point for passing or failing the test has been changed to 80 percent. Recalculate the B-index, agreement statistic, and item phi for each item. Be sure to carry out and round all operations to three places to the right of the decimal point instead of the two places that we have been using in the examples. Record your answers in the spaces provided in Table 4.15. How would you interpret these new indexes? And, how do they compare to the results that were obtained when the cut-point was 70 percent (see Table 4.9)?

TABLE 4.14: ITEM ANALYSIS DATA (FIRST 10 ITEMS ONLY) FOR APPLICATIONS EXERCISE

TABLE 4.15: ANSWERS FOR APPLICATION EXERCISE C

ITEM                    ITEMS
STATISTIC      1 2 3 4 5 6 7 8 9 10

IFtotal
IFpassed
IFfailed
B
A
Ø