On the probability of making Type I errors.

A statistical test leads to a Type I error whenever it leads to the rejection of a null hypothesis that is in fact true. The probability of making a Type I error can be characterized in the following 3 ways: the conditional prior probability, the overall prior probability, and the conditional posterior probability. In this article, we show (a) that the alpha level can be equated with the 1st of these and (b) that it provides an upper bound for the second but (c) that it does not provide an estimate of the third, although it is commonly assumed to do so. We trace the source of this erroneous assumption first to statistical texts used by psychologists, which are generally ambiguous about which of the 3 interpretations is intended at any point in their discussions of Type I errors and which typically confound the conditional prior and posterior probabilities. Underlying this, however, is a more general fallacy in reasoning about probabilities, and we suggest that this may be the result of erroneous inferences about probabilistic conditional statements. Finally, we consider the possibility of estimating the (posterior) probability of a Type I error in situations in which the null hypothesis is rejected and, hence, the proportion of statistically significant results that may be Type I errors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The ancestry of the surrogate mother.

Comments on the awarding of the American Psychological Foundation's Gold Medal Award for 1973 to H. F. Harlow. This well-deserved honor is based in part on Harlow's contributions (e.g., Harlow et al, 1971) to developmental psychology and primatology, including the use of the surrogate mother technique. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the functional relationship between word identification and letter probability.

Investigated whether words made up of probable letters and probable letter combinations are more accurately recognized than words made up of improbable letters and improbable letter combinations. The experimental method corrected shortcomings in previous research which has shown accuracy of word recognition to be affected only by word probability and not by letter probability. The shortcomings were the confounding of different letter probability dimensions within one another. In the present investigation with 40 19-43 yr old adults, 100 words were assessed with respect to the probabilities of their letters and, independently, the conditional probabilities of their letters. Subsequent tests of recognition accuracy in a brief presentation showed accuracy to be greatest for words made up of letters having either high simple probabilities or high conditional probabilities. It is concluded that word recognition is an active, perhaps serial, process which makes liberal use of individual letter statistics to facilitate accurate recognition. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

East Gondwana ancestry of the sunflower alliance of families

The sunflower alliance of families comprises nearly 10% of all flowering plant species and includes the largest of all plant families, the sunflower family Asteraceae, which has 23,000 species, and the bellflower family Campanulaceae. Both are worldwide in distribution, but the majority of their species occur in the northern hemisphere. Recently it has been shown that a number of small, woody families from the Australian-Southwest Pacific area also belong in this relationship. Here we add yet another such family and present phylogenetic, biogeographic, and chronological analyses elucidating the origin of this large group of plants. We show that the ancestral lineages are confined to Malesia, Australia, New Guinea, and New Zealand and that the sunflower and bellflower families represent phylogenetically derived lineages within a larger group with a Cretaceous and southern-hemisphere, presumably East Gondwana, ancestry. Their highly derived position in the flowering plant phylogeny makes this significant for understanding the evolution of flowering plants in general.     

On the evaluation of probability judgments: Calibration, resolution, and monotonicity.

Judgments of probability are commonly evaluated by 2 criteria: (1) calibration, namely, the correspondence between stated confidence and rate of occurrence, and (2) resolution, namely, the ability to distinguish between events that do and do not occur. Two representations of probability judgments are contrasted: the designated form that presupposes a particular coding of outcomes (e.g., rain vs no rain) and the inclusive form that incorporates all events and their complements. It is shown that the indices of calibration and resolution derived from these representations measure different characteristics of judgment. Calibration is distinguished from 2 types of overconfidence: specific and generic. An ordinal measure of performance is proposed and compared to the standard measures in forecasts of recession and in both numerical and verbal assessments of general knowledge. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Migrating monopredominant arthritis in children of Assyrian ancestry

We describe an unusual form of arthritis affecting 3 Assyrian children to inspire a search for further cases to determine how unique it may be. After different patterns of onset, 3 of 4 children with arthritis from the Assyrian community in northern California had an unusual course of recurrent arthritis, predominantly in one joint at a time. There was rapid cartilage and bone destruction in involved joints. The 3 children are HLA-DR4. The 4th patient had a more typical childhood polyarticular course. Two of the first 3 patients had fever with attacks. None had rheumatoid factor, antinuclear antibody, or the HLA-B27 antigen. This unusual, severe, monopredominant but migrating arthritis appears to be particularly associated with Assyrian descent.     

On the relation between the probability of a word as an association and in general linguistic usage.

"The summed associative probability of a word, measured by its total frequency in the Kent-Rosanoff tables, is considered in relation to the probability of emission of the word in general linguistic usage, measured by its frequency in the Lorge magazine count. 2 features stand out in the data: A high positive correlation (.94) for magazine-count frequencies of less than 800; and a sharp reversal in this relationship for higher magazine-count frequencies… . The high correlation found for all other words indicates that the average probability that a given word will be emitted as a response in the word-association experiment is the same as its probability in general discourse." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Bioelectrical impedance analysis and anthropometry in Ecuadorian children of African ancestry

In the city of Esmeraldas, north-western coast of Ecuador, height, weight, and body composition of 600 male and female schoolchildren of African ancestry in the age groups four, five and six years were investigated. All the children were apparently healthy without any obvious or reported pathologies and in accordance with data from personal information were assigned to one of two socio-economic classes. The greater values for weight and height shown by children in the higher socio-economic group than in the less well off are compatible with those for more fat and water as obtained by the BIA investigation. Additional information on nutritional, muscular and general health status was obtained from positioning and degree of dispersion of the 'Biagram' ellipses. It seems that both the anthropometric and the bioelectrical impedance methods provide useful information on the differences due to belonging to one or other of the socio-economic groups.     

Measuring the vague meanings of probability terms.

Assessed membership functions over the [0,1] probability interval for several vague meanings of probability terms (e.g., doubtful, probable, likely), using a modified pair-comparison procedure in 2 experiments with 20 and 8 graduate business students, respectively. Ss performed 2 tasks in both experiments: They judged (A) to what degree one probability rather than another was better described by a given probability term and (B) to what degree one term rather than another better described a specified probability. Probabilities were displayed as relative areas on spinners. Task A data were analyzed from the perspective of conjoint-measurement theory, and membership function values were obtained for each term according to various scaling models. Findings show that the conjoint-measurement axioms were well satisfied and goodness-of-fit measures for the scaling procedures were high. Individual differences were large but stable, and the derived membership function values satisfactorily predicted the judgments independently obtained in Task B. Results indicated that the scaled values represented the vague meanings of the terms to the individual Ss in the present experimental context. (51 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Celtic ancestry, HLA phenotype and increased risk of skin cancer

Individuals of Celtic ancestry are claimed to be at greater risk of skin cancer than non-Celts, and various positive and negative associations between certain human leucocyte antigen (HLA) phenotypes and the development of skin cancer have been described. The aims of this study were to determine whether any HLA phenotypes are associated either with Celtic or non-Celtic ancestry, or skin type. One thousand and ten members of the Welsh Bone Marrow Donor Registry (WBMDR), whose HLA phenotypes are known, were asked to complete a questionnaire which enquired as to their family origins and their 'Index of Celtic Ancestry' scored out of 12. Three groups were identified: non-Celts (score < 3), Celts (score > 9), and a subset of the Celts--'high scoring' Celts (score > 10). Details of hair and eye colour and skin type were also requested. Skin type and HLA-A, -B, -DR and -DQ frequencies were compared between the three groups (Celts, non-Celts and 'high scoring' Celts), and a random indigenous population of 9196 members of the WBMDR. Seven hundred and thirty-six replies were received (279 male, 457 female, mean age 31 years). One hundred and forty-four Celts, 51 'high scoring' Celts and 170 non-Celts were identified. Forty-six (32%) Celts had skin type I or II compared with 36 (21%) non-Celts (P = 0.039), and 37 (73%) 'high scoring' Celts had skin type I or II (P < 0.0001). However, there were no significant differences between the groups with regard to hair colour, eye colour or number of episodes of painful sunburn. The frequency of HLA-DR4 was 32% in the non-Celtic group, 44% in the Celtic group (not significant), and 53% in the 'high scoring' Celts (P = 0.008). However, the difference was not significant after correction. There were no significant associations between skin type and HLA phenotype. HLA-DR4 is known to be associated with an increased risk of both basal cell carcinoma and malignant melanoma and its increased frequency in Celts may be an independent risk factor for skin cancer in addition to skin type.     

Comparison of skin reflectances between Bolivian lowlanders and highlanders of European ancestry

I compared one genetic marker, skin reflectances, between Bolivians of European ancestry residing at high altitude in La Paz (3600 m; 41 boys and 65 girls) and at low altitude in Santa Cruz (400 m; 140 boys and 117 girls). Reflectances were measured at three wavelengths (425 nm, 545 nm, and 685 nm) on two different sites: the medial surface of the inner upper arm and the forehead. Principal components analysis was used to reduce age-, sex-, and surname-standardized reflectances to three independent components. The first principal component, which assesses the genetic component of melanin concentration, did not differ between samples, indicating that there are no significant differences between lowland and highland Bolivians of European ancestry with respect to the genetic component of skin reflectances. The second principal component, which assesses the influence of tanning on skin reflectance, also did not differ significantly between highlanders and lowlanders. Finally, the third principal component, which assesses the impact of vascularity on skin reflectance, was significantly lower in residents of La Paz than in residents of Santa Cruz, suggesting a greater vascularity-induced darkening of skin color in highlanders than lowlanders, possibly reflecting the higher hemoglobin concentrations that are typical of highland populations.