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310 appendix a: overview of pirls 2006 procedures
relationship between the two reading purposes in each of the PIRLS 2006
countries and between the two processes of comprehension. Across
countries, the median correlation between reading for literary experience and
reading for information was 0.88, and the median correlation between the
comprehension processes retrieving and simple inferencing and interpreting,
integrating, and evaluating was 0.92.
To facilitate comparisons of countries’ relative performance on the
two reading purposes (i.e., do students perform relatively better reading
for literary experience or reading for information?) and on the two
comprehension processes (again, do students perform relatively better
on one process than the other?) PIRLS 2006 set all scales to have the same
scale average and standard deviation—500 with a standard deviation of
100. This means that any existing differences in the overall difficulty of the
items comprising each of the scales are adjusted statistically to be equal
in the interests of making relative comparisons. That is, the differences in
performance among countries reflect differences in student achievement that
would be expected on sets of items of equal difficulty.
To give an indication of the difficulty of the reading purpose and process
scales, Exhibit A.16 presents the percentage of students responding correctly
to each item, averaged across the items for each scale, for each participant.
From this exhibit it may be seen that the items making up the literary and
informational scales are similar in difficulty—55 percent correct, on average
across all participants, for literary reading and 52 percent correct, on average,
for informational reading. However, there is a much greater difference in
average difficulty between the two scales for the comprehension processes.
The average percent correct for the items on the retrieval and straightforward
inferencing scale was 64 percent, compared with an average percent correct
of just 44 percent for the interpreting, integrating, and evaluating items.
The items making up the interpreting, integrating, and evaluating
scale were particularly difficult for students in Kuwait, Morocco, Qatar, and
South Africa, where the average percentage of students answering the items
correctly ranged from 11 to 14 percent. With average achievement as low as