Underestimation Error Research Articles

Bioassay of clindamycin in bile.

This study compares different preparations of standard solutions for determining clindamycin in bile. Pooled human serum, ox bile, 10% human bile, and 0.1 M phosphate buffer were compared, and pooled human bile was serving as reference standard curve. The use of pooled human serum and ox bile resulted in a considerable error of overestimation of clindamycin in bile. An error of underestimation occurred when 10% human bile or 0.1 M phosphate buffer was used as a standard solution. It is concluded that none of the different preparations tested are acceptable substitutes for human bile.

Poisoning cases: suicide or accidents.

The accurate classification of causes of death is fundamental to progress in preventive medicine. Classifying death by poisoning may be specially difficult because the exact distinction between deliberate and accidental poisoning is inherently difficult for the coroner to make. Thus figures for suicidal poisoning are likely to be under-estimated because of ambiguous evidence and because of the stringent legal definition of suicide which coroners must apply. An examination of the drugs involved in poisoning cases, comparing their frequencies in the suicide and accident categories, may throw some light on the validity of coroners' present methods of classifying and provide evidence about the limits of error of under-estimation of the suicide rate.

Surface colouration, lettering and referential dimension of traffic marker perception.

5 experimental traffic markers differentiated with respect to colouration and lettering were each presented at 7 angles of orientation randomly repeated 5 times. 5 groups comprising 15 drivers per group gave judgments of shape and slant. It was found that signalling aspects of the marker (form, colouration and lettering) produced significant differences upon apparent shape. Differences in slant perception were not dependent upon the three signalling characteristics. Consistent with prior research, the reference aspect of the marker (angle of orientation) produced large errors of underestimation particularly at the most acute angles. The perceptual functions suggest that systematic differences separate physical and psychological spaces.

Drivers' judgments in overtaking and passing.

Drivers' judgments in vehicular overtaking and passing were studied using familiar (drivers' own) cars and an unfamiliar government vehicle at speeds of 18, 30, and 50 mph. Drivers were not able to estimate passing distances accurately. Average errors of estimation for the different conditions varied from 20 to 50% of the actual overtaking distance. Errors of underestimation, where the maneuver required more space than judged, increased with speed. At 18 mph, 15% of the estimates made by drivers were underestimates: at 50 mph 68% were underestimates. There were no differences observed attributable to familiarity with the car.

A theory of the Mueller-Lyer illusion.

The Mueller-Lyer illusion is explained on the basis of the central tendency effect which refers to errors of overestimation and underestimation that occur whenever repeated judgments of a series of stimuli are made. It was noted that the theory could be extended to explain some, but not all, other types of geometrical illusions.

A comparison of different survey techniques for obtaining vital data in A developing country

This article presents estimates of the sources and the extent of observation errors in different questionnaires and methods used to collect birth and death data in the 1961-63 multi-purpose sample survey of Morocco.The questionnaires used in the analysis of the three survey rounds were a list of household members (Rounds1 and 2) and a roll-call (Round3); retrospective death (Rounds1, 2, and 3) and birth (Round 3) queries; a date-of-birth tabulation (Round 2); and a household check-sheet to explain differences between Rounds 1 and 2. All available questionnaires for a given household were brought together and collated to provide several sources of information on births and deaths and a basis for assessing errors.From this analysis, the survey attempted to define the nature and to estimate the frequency of the errors which would have occurred if more restricted types of survey design had been used. Results, based on the period between Rounds 1 and 2, led to three major conclusions.First, if vital data had been collected with a single-round retrospective procedure, gross error (over enumeration plus underenumeration) would have been 17 percent for births and 36 percent for deaths. There is a net error of overenumeration of 3 percent for births (1.4 per1,000population) and 9 percent for deaths (2.3 per1,000population).Second, if two rounds were available to permit a combination of household composition follow-up and a retrospective mortality questionnaire, overenumeration would be almost entirely eliminated and underenumeration would be noticeably reduced. Third, most of the remaining errors of underestimation may be attributed to (1) an estimated number of infants born and deceased between two rounds and missed by all questionnaires, (2) matching failures caused by the absence of adults at Round 1, and (3) matching errors.

Texture of the stimulus field and age as variables in the perception of relative distance in photographic slides

The perception of relative distance in the third dimension, on the basis of photographic stimulus fields, was studied in children in Grades 1, 4, 8, and 9, and college adults. Photographic slides were made of stimulus fields constructed to represent four degrees of texture density and four degrees of regularity of patterning of the texture elements. For each texture the perceived midpoint of a standard distance was determined by means of an adaptation of the method of constant stimuli. The results indicated a general error of underestimation (underconstancy), which decreased some-what with age. At all age levels this error decreased as texture density increased, but there was no significant interaction between age and texture. Regularity of patterning produced less consistent effects, though there was an over-all increase in constancy from the least to the most regular pattern. The judgments showed a high degree of consistency at all age levels, pointing to the advantages of this type of psychophysical method for the study of perceptual judgments in children.

Nonvisual perception of the postural vertical. I. Sagittal plane.

Abstract : The three experiments reported here were tests of the effects of four variables upon the perception of the postural upright following body tilt in a forward or backward direction. The four variables studied were; (1) the degree of initial tilt, i.e., the degree to which the subject was tilted before being moved toward the vertical, (2) the time held at initial tilt, (3) the direction of initial tilt, and (4) the angular velocity of return. The fourth variable investigated in the present experiments, velocity of return, had not been evaluated before, nor had any one of the other three variables been studied systematically in the sagittal plane. Immediately bearing on the present report are certain studies dealing with the non-visual perception of the upright, most of which were conducted using lateral tilt. Briefly these reveal that: (a) the error of judgment of the upright is directly determined by the degree of initial tilt, increasing as an underestimation of the upright as the magnitude of initial tilt increases. (b) the error of judgment, either as an underestimation or an over-estimation of the vertical, does not differ significantly for the two directions of initial tilt within any one plane. (c) the error of underestimation of the vertical increases as the time held at the initial tilt increases.