Null hypothesis significance testing: a review of an old and continuing controversy.

Null hypothesis significance testing (NHST) is arguably the most widely used approach to hypothesis evaluation among behavioral and social scientists. It is also very controversial. A major concern expressed by critics is that such testing is misunderstood by many of those who use it. Several other objections to its use have also been raised. In this article the author reviews and comments on the claimed misunderstandings as well as on other criticisms of the approach, and he notes arguments that have been advanced in support of NHST. Alternatives and supplements to NHST are considered, as are several related recommendations regarding the interpretation of experimental data. The concluding opinion is that NHST is easily misunderstood and misused but that when applied with good judgment it can be an effective aid to the interpretation of experimental data.

Speech quality evaluation using "phoneme-specific" sentences.

A new approach is described for the design of speech materials used in subjective speech quality evaluation. Speech sounds are classified by their acoustic properties, and sentences are composed so as to concentrate all sounds with similar properties within one sentence. As a test of the method, subjective quality data were collected, using both a rank ordering and a rating task, from a set of 12 linear predictive vocoders, whose parameters were chosen so as to equate their bit rates at 2600 bps. The results show that the method can reliably reveal small differences in quality, and also yields information that can be of diagnostic help in determining the causes of quality degradation by a particular vocoder. A set of phoneme-specific sentences is appended.

Context is important but it does not explain everything: a comment on "Matching performance and the similarity structure of the stimulus set" by Crist.

Crist's experiments provide convincing evidence of the importance of context in letter-matching tasks. His detailed analysis also demonstrates how the reporting of central tendency measures on data aggregated over different stimuli can sometimes lead to an oversimplified view of the processes involved. His rationale for the experiments and his theoretical treatment of his results are criticized in this review, however, as unnecessarily polarizing the analytic and contextual views of perceptual matching and as overstating the case for context as a sufficient explanatory construct. Crist's results suggest both general and specific contextual similarity effects; a possible theoretical account is outlined.

The Framingham Eye Study. II. Association of ophthalmic pathology with single variables previously measured in the Framingham Heart Study.

Using the age-sex-specific data collected in the Framingham Heart Study 1948--1964 together with ophthalmic diagnoses made in the Framingham Eye Study in 1973--1975, the following variables were found to be associated with senile cataract: education, casual blood sugar, systemic blood pressure, height, vital capacity, serum phospholipid and hand strength; with senile macular degeneration: systemic blood pressure, height, vital capacity, left ventricular hypertrophy, hand strength and history of lung infection; with diabetic retinopathy: casual blood sugar, urine sugar and other specific elements of diabetes; with ocular hypertension: systemic blood pressure, height, casual blood sugar and pulse rate. No variables were identified as associated with open-angle glaucoma. The paper stresses the need for corroboration of these findings, which may be a mix of real and chance associations, and the need for additional analyses before any of these associations are considered evidence of factors related to risk of ophthalmic disease.

The Framingham Eye Study. I. Outline and major prevalence findings.

During the period 1973--1975, 2675 out of 3977 still-living members of the Framingham, Massachusetts, study population, who have been under investigation for coronary disease risk factors since 1948 and who were in 1973--1975 aged 52 to 85, were given an eye examination stressing cataract, diabetic retinopathy, macular degeneration and glaucoma. Of 2940 subjects who still lived in the local Framingham area, 2477 were examined. Local population prevalence for one or both eyes positive was: 15.5% for senile cataract, 3.1% for diabetic retinopathy, 8.8% for senile macular degeneration and 3.3% for open-angle glaucoma. The proportion of adults with poor "best" visual acuity may be much less than has been estimated by the National Health Survey and the proportion with open-angle glaucoma much more than currently suspected on the basis of foreign studies.

Assessment of nasalization in the speech of deaf children.

Nasality is widely recognized as a problem in the speech of many deaf people. This paper describes one approach to the assessment of nasalization and to the development of visual aids to assist in training of velopharyngeal control. The approach involves detection of the velopharyngeal opening during voiced sounds by means of a small accelerometer attached to the nose, and presentation of the accelerometer output on a computer-controlled visual display. The display may be used as a training aid, or for the purpose of analyzing either recorded or live speech. Objective data are presented on some of the properties of the accelerometer output for the speech of people with normal hearing and of a number of children whose hearing is severely impaired. These data show inadequate velopharyngeal control, particularly improper nasalization of certain vowels, for a significant number of the deaf children. For a group of the hearing-impaired children, subjective judgments of the adequacy of velopharyngeal control and of other speech attributes were obtained. Correlations among these judgments and relations between judgments of adequacy of velopharyngeal control and the objective measures of nasalization are shown. Some comments are made on the development of procedures for the training of velopharyngeal control using the display as an aid.

Computer-aided speech training for the deaf.

An effort to develop a computer-based system of speech-training aids for the deaf is reported. The system is described, as are four different types of visual displays that have been programmed to date. The use of the system in a school for the deaf and an attempt to evaluate its effectiveness are described. The importance of close collaboration between researchers and teachers on efforts to develop innovative training aids is emphasized, as is the need to resolve some basic pedagogical issues.

Can characters be classified directly as digits vs letters or must they be identified first?

Two experiments were addressed to the question of whether or not Ss can distinguish between letters and digits without identifying the characters. In Experiment I Ss attempted to identify noisy characters; a character was said to be implicitly classified correctly if the identification response, whether correct or incorrect, was in the same category vis-a-vis the letter-digit distinction as the stimulus. Implicit classification of characters for which the identification response was incorrect was very little better than chance. The task in Experiment II was to classify the characters directly. The explicit classification performance in this case was poorer than the implicit classification performance of Experiment I. The results were taken as evidence that Ss could not distinguish between letters and digits unless they could identify the characters.