Norms and Sex Differences for the Standard Progressive Matrices in Libya
Al-Shahomee, Alsedig Abdalgadr, Lynn, Richard, Mankind Quarterly
Results are reported for a standardization of the Standard Progressive Matrices in Libya. The sample consisted of 1800 children, comprising 180 (90 boys and 90 girls) for each year of age for 8-17 year olds. The test had high reliability and adequate validity. Factor analysis revealed the presence of a strong general factor interpreted as Spearman's g. Girls obtained a significantly higher mean than boys at age 10, while boys obtained higher means at ages 15 through 17. The variability was generally greater among girls than among boys. In relation to British norms, the sample obtained a mean IQ of 82.7, which is reduced to 78 if an adjustment is made for a Flynn effect increase in Britain of 2 IQ points per decade. The younger Libyan children performed better than older children, relative to British norms.
Key Words: Intelligence; Progressive Matrices; Libya; Sex differences; Variability.
Raven's Progressive Matrices test (RPM, Raven, 1939; Raven et al., 2000) is the most widely used test of intelligence in numerous countries throughout the world. Several hundred studies that have used the test are summarized in Lynn (2006). One reason for the popularity of the test is that it is non-verbal and can therefore be applied cross-culturally, while verbal tests are more culture specific and preclude cross-cultural comparisons. Another reason for the popularity of the test is that it is considered to be an excellent test of g, the general factor present in all cognitive tasks that was first identified by Spearman (1904) and is largely a measure of reasoning ability (e.g. Carroll, 1993; Jensen, 1998; McGrew & Flanagan, 1998).
Although the Progressive Matrices have been administered in many countries, few studies have been done in the countries of North Africa. The only countries in this region for which normative data exist are Egypt, Tunisia, and Libya. Abdel-Khalek (1988) reported normative data for the Standard Progressive Matrices for Egypt, on which Egyptian children obtained an average British IQ of 83. Normative intelligence data for Tunisia have been reported by Abdel-Khalek & Raven (2006). The results come from a standardization of the Standard Progressive Matrices on adults carried out in 2001.The sample size was 509 and a score of 47 is given as the 50th percentile of 20 year olds, together with a score of 54 for British 20 year olds obtained in the 1992 standardization. The raw score difference of 7 is equivalent to approximately 14 IQ points, giving the Tunisian sample an IQ of 86. If a Flynn effect adjustment is made for an increase in the British IQ of 2 IQ points per decade, the British IQ will have increased by 2 IQ points from 1992 to 2001. Hence the difference between Britain and Tunisia will become 16 IQ points, reducing the Tunisian mean to 84, in relation to a British IQ of 100.
A further calculation of the IQ in Tunisia has been made by Rindermann (2007). He adopted scores obtained in the 2003 PISA study of mathematics in 15 year old school students as a measure of intelligence. In this study the mean score of school students in 29 economically developed OECD countries was 489 (sd=104), and the mean score of Tunisian school students was 359 (sd=82). The difference between the economically developed countries and the Tunisians is 1.40 sd units, equivalent to an IQ difference of 21 IQ points, and therefore giving an IQ of 79 for Tunisia in relation to 100 for the 29 OECD countries. This calculation confirms earlier studies reviewed in Lynn & Vanhanen (2002, 2006) showing that the use of tests of mathematics as proxies for intelligence tends to magnify the between-country differences obtained from IQ tests. A more recent study of 86 countries found that the standard deviation between countries, relative to standard deviations within countries, was nearly 49% larger for scholastic achievement tests than for "IQ tests" (Lynn & Meisenberg, in press). Nevertheless, the results from the Standard Progressive Matrices and from the mathematics test are broadly consistent for Tunisia, giving IQs of 84 and 79, respectively. …