Interpreting results of students who are outside the norms range

LASS 11-15 is normed for use with students in the age range 11 years 0 months to 15 years 11 months. Over the age of 15:11, LASS 11-15 raw scores and pass rates will not conform to a normal distribution because many students will achieve a maximum or near-maximum performance (in statistical terms this is sometimes referred to as a ‘ceiling effect’). Similarly, below 11:0, most students will obtain very low scores on the LASS 11-15 tests, which will create a bunching of scores at the lower end of the distribution (sometimes called a ‘floor effect’). When ceiling and floor effects occur in any test, it is not a good discriminator between students with differing abilities. 

Therefore, LASS should only be used psychometrically (i.e. to compare a given student’s performance with that of other students of the same age) within the specified age range of the test. However, outside this age range LASS can have a certain limited value if used clinically (i.e. to identify students with particular difficulties), or ipsatively (i.e. to compare a given student’s performance on one test with the same student’s performance on another). When employed in this way with older or younger individuals, it should always be used with extreme caution, and then only by experienced professionals who fully appreciate the limits within which they are working. Many adults with significant cognitive problems (e.g. dyslexia) are likely to experience difficulties on some LASS tests. Nevertheless, this is not necessarily the case. When used with adults, absence of any indications of difficulty on LASS tests must never be taken as evidence that there are no underlying difficulties because the tests may just not be sensitive enough. In any case, adults typically develop strategies by which they can compensate for any cognitive limitations, and these can have a masking effect, preventing any limitations from showing up in assessments.

The preferred solution to assessment of students older than 15 years 11 months is to use Lucid’s adult screening systems (LADS) which is designed for ages 16 years upwards. Students younger that 11:0 should be assessed with LASS 8-11 (8:0–11:11) or CoPS Cognitive Profiling System (4:0–8:11). For more information on these assessment products, contact Lucid Research Limited or visit www.lucid-research.com.

Under exceptional circumstances, age equivalent scores can be used when assessing students outside the norm range. An age equivalent is defined as the chronological age range of students that would be expected to achieve a given raw score. Note, however, that as three of the LASS 11-15 tests are adaptive, the adaptive score rather than the raw score should be used for calculating age equivalents in these cases.

Age equivalents are designed to be used only in exceptional circumstances, e.g. for students in special education where centile norms are not always helpful. Age equivalents should not be used routinely in cases where centile norms are applicable, because age equivalents give only a very rough approximation of the student’s ability. The term ‘age equivalent’ should also be applied with caution. It can be insulting for adults to be described in terms of age equivalents (e.g. as having a reading age of so-and-so), which might be misinterpreted as implying that they are to be treated like children, rather than grown-ups.

To determine an age equivalent for any LASS score see Section 9.4. Note that it is not possible to provide age equivalents for the Single Word Reading test. This is because the scores for this test are not distributed in a normal curve — in fact, there is a significant negative skew — indicating strong ceiling effects. This is explained in Section 2.2.2.

Example A

Tina, chronological age 17 years 6 months, has moderate learning difficulties. Her measured IQ on WAIS-III was 68, which places her in the lowest 3% of her age group in intelligence terms. Her teacher wants to know what level of texts she might be able to cope with and also what are her relative strengths and weaknesses in learning. Tina has an adaptive score of 0.8720 on Sentence Reading and raw scores of 31 on Cave and 5 on Mobile. Her centile scores for these tests shown on the LASS Graphical Profile were, respectively, 20, 48 and 26, but of course the norms will automatically compare her with normal 15 year-olds. Referring to the table in Section 9.4, it can be seen that on Sentence Reading Tina’s score places her within the 11:0–11:5 age range, which, although low for her age, indicates that she should be able to manage texts at around Year 6 level (Grade 6). On Cave Tina is at the 13:6–13:11 range, while on Mobile she is in the 11:0–11:11 range. In fact, it appears that visual memory is a relative strength for Tina, and hence her teachers can make good use of that in learning and teaching. Indeed, it is quite likely that it is her strong visual memory that has enabled her to maintain a reasonable reading ability despite her rather low overall intellectual level. 

Example B

Craig is a very bright boy aged 9 years 6 months. His reading skills are believed to be at least three years ahead of his chronological age level. However, his teacher wants to know whether the cognitive skills that underpin reading are as well developed. The teacher administers LASS 1115, finding that Craig obtains raw scores of 30 on Cave, 4 on Mobile, and 9 on Nonwords. The LASS 11-15 Graphical Profile gives centile scores of 55, 20 and 38, respectively for these tests, which is not particularly helpful as these compare Craig’s results with that of eleven-year-olds. Referring to the table in Section 9.4, it can seen that he is at the 13:0–13:6 age level for Cave, but less than the 11:0 age level for Mobile and at the 11:0–11:6 level for Nonwords. From this is can be deduced that Craig is probably relying heavily on visual memory when reading and that his phonic skills are not quite as good as might have been expected. A relevant factor would appear to be his auditory-verbal memory, which although above average, is probably not in step with his overall intelligence.