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Where Is Kg on the Baby Weight Scales

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Accuracy and consistency of weights provided by home bathroom scales

  • Kim Spaccarotellai,
  • Jennifer Martin-Biggersane,
  • Virginia Quickii &
  • Ballad Byrd-Bredbenner1

BMC Public Health volume thirteen, Article number:1194 (2013) Cite this article

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Abstract

Groundwork

Self-reported body weight is oft used for calculation of Torso Mass Index considering it is easy to collect. Picayune is known nigh sources of mistake introduced by using bath scales to measure weight at home. The objective of this study was to evaluate the accurateness and consistency of digital versus dial-type bathroom scales commonly used for self-reported weight.

Methods

Participants brought operation bath scales (n = xviii dial-type, n = 43 digital-type) to a central location. Trained researchers assessed accuracy and consistency using certified calibration weights at x kg, 25 kg, 50 kg, 75 kg, 100 kg, and 110 kg. Information also were nerveless on frequency of scale, historic period and floor surface below the scale.

Results

All participants reported using their scale on difficult surface flooring. Earlier calibration, all digital scales displayed 0, but punch scales displayed a mean absolute initial weight of 0.95 (1.9 SD) kg. Digital scales accurately weighed exam loads whereas punch-blazon scale weights differed significantly (p < 0.05). Imprecision of dial scales was significantly greater than that of digital scales at all weights (p < 0.05). Accuracy and precision did non vary by scale historic period.

Conclusions

Digital abode bathroom scales provide sufficiently accurate and consistent weights for public health research. Reminders to zilch scales earlier each use may further meliorate accurateness of self-reported weight.

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Background

Self-reported heights and weights are ofttimes used in public health research with adults, children and families because these data are easy and inexpensive to collect [1]. However, self-reported and good-measured weights may differ by factors such every bit historic period, sexual activity, and perceived weight status [2–4]. In addition to parents reporting their own weight, they also may be asked to report the weight of their children. A kid'due south weight condition as well every bit parental perception of their child's weight impact accuracy of reports [4, 5]. A recent study reported that parents of overweight children ages ii to 6 years old erroneously overestimated their kid'southward weight, only parents of older overweight children and adolescents underestimated their child's weight [four]. Similar findings were reported using information from ii nationally representative surveys [6]. Others have noted mothers underestimate kid weight [7, 8].

Inaccuracies in reported weights often are attributed to social desirability and/or erroneous measurements or recalls [ane, ix, 10]. Minimal research, however, has examined the accuracy of a common tool used to mensurate self-reported weights, that is, dwelling house bath scales. The express available data suggest that dwelling scales, likewise every bit medical class scales used past physicians, tin can vary in accuracy and precision [11]. A study of 37 dial-type bathroom scales in British clinics reported inaccuracies of more than 1% compared with a calibrated electronic scale, suggesting that digital scales may be more accurate [12]. Further, an evaluation of 233 scales (type not specified) from United States primary care, diabetology and endocrinology clinics, and fitness and weight loss centers establish that more than than a quarter of the scales were more than 0.9 kg imprecise when tested with a 45.5 kg standard weight. At 113.6 kg, about one in five scales was imprecise past more than 2.7 kg, or most 1 Body Mass Index (BMI) unit of measurement [10]. Several factors, such every bit type of floor, foot placement on the scale, and type of wear or shoes worn during weighing, may influence accurateness of scales [13].

Widespread implementation of customs-based obesity prevention programs targeting children and families is currently underway [14–16]. Some of these programs, and the research used to develop them, rely on self-reported weight or BMI, which is calculated using weight and reported as a primary outcome or measure of intervention effectiveness [14, 17, xviii]. A major limitation to establishing intervention (in)effectiveness is inaccurate weight reports [i, 19, twenty]. To accelerate the work of public wellness professionals in implementing effective programming aimed at ameliorating the obesity epidemic, it is important to increase the accuracy of self-reports. Thus, the goal of this study was to assess the accuracy of home bath scales to amend understand how their utilize in the common procedure of self-weighing may affect accuracy of self-reported weight data [21].

Methods

Participants and process

Notices were posted to recruit study participants from the university campus. Participants included faculty, staff, students and parents of children attending a preschool run past the university. The Rutgers University Institutional Review Lath approved the procedures, and all participants gave informed consent.

Participants brought their functioning home bath calibration to a primal location for assessment and completed a questionnaire describing the scale'south age, type of flooring in the location where the scale is used in the home, frequency of use, and calibration history. Trained researchers recorded scale condition (i.due east., new, light wear, heavily worn or outward evidence of harm), type (i.e., dial or digital), units and increments of measurement, maximum capacity, and weight displayed upon arrival at the testing site.

The procedure for evaluating calibration accuracy was modeled on previous research [10]. The accuracy of scales in measuring weight load was assessed using National Constitute of Standards and Technology (NIST) Class F calibration weights at the post-obit exam loads: 10 kg, 25 kg, l kg, 75 kg, 100 kg, and 110 kg. To make up one's mind accuracy in measuring weight distribution (i.e., distributed over a man body or concentrated in a calibration weight), two humans were weighed in addition to the calibration weights (i.east., one researcher and a second researcher holding a 10 kg scale weight close to the body between the waist and hips). To make up one's mind consistency in weight measurements, all weight assessments were measured in duplicate (Round 1 and Circular ii). During Round 1, each calibration was used to assess eight loads: the two researchers and the 6 calibration weights. Round 2 was the aforementioned as Round 1 and was conducted immediately afterward Round 1. At the end of each Round ii, a calibrated research calibration was used to weigh in duplicate the first researcher and the second researcher property a ten kg calibration weight close to the body between the waist and hips. The calibrated research calibration weights were used as the "standard" for comparing the two researcher weights registered by the home scale. The NIST calibration weights served as their own comparison to those registered past the home scale. Prior to Round 1 and in between each examination load as necessary, all scales were calibrated to annals zero when no weight was practical. Data were recorded in real time using a computerized spreadsheet.

Statistical analysis

Data were analyzed using SPSS version 21.0 (Chicago, IL). Paired samples t-tests were used to exam for differences in scale consistency between Circular 1 and 2. One group t-tests were used to estimate differences betwixt the displayed weight and bodily weights of the calibration weights. Unpaired t-tests were used to guess the precision between different types of scales, and multinomial regression was used to examine the percent of digital versus dial scales with various degrees of weight imprecision. Absolute weights were used to avoid the possibility of underweight errors canceling out overweight errors. Differences were considered significant at p < 0.05. Values are reported as ways and standard deviations (SD) unless otherwise noted.

Results

Of the 67 bath scales that were received, 6 scales were eliminated due to damage or improper functioning (i.e. did not register a value when tested with the calibration weights) or because they were non a home scale. Of the final sample (due north = 61), 18 were dial (xxx%) and 43 (seventy%) were digital scales from 16 various manufacturers. All were new, like new, or had lite vesture. The bathroom scales' precision increments were 0.045 kg, 0.091 kg., 0.fifteen kg, and 0.45 kg (21%, 38%, 13%, and 28%, respectively). The maximum weight capacities ranged from 123 kg to 181 kg, with the well-nigh mutual capacity being 136 kg (35%). Dial scales were significantly older (p = 0.042; hateful historic period 6.0 (vi.9 SD) years old) than digital scales (mean historic period iii.half-dozen (ii.3 SD) years old). When the scales were first observed, all digital scales displayed 0, whereas dial scales displayed a hateful absolute weight of 0.95 (1.9 SD) kg, with a range of -0.45 to seven.nine kg.

All participants reported using their bathroom scale on difficult flooring. Scales were used daily (21%), weekly (46%), or monthly (27%), and 5% used their scale yearly or less than one time a year. Participants reported infrequently calibrating their calibration; simply 28% calibrated the scale each time or most of the time before using it. Of these participants, 64% had dial-type scales.

Mean weight between Rounds 1 and 2 differed significantly only for dial scales tested with a 75 kg calibration weight (p = 0.028). For all other examination loads, scales consistently registered the aforementioned weight, regardless of the scale type and load. Per 45.iv kg, the difference in accented weight registered between Round i and two averaged approximately 0.xi kg (range from 0.0 kg to 0.6 kg), with the largest errors for the ten kg calibration weight.

Tabular array 1 compares accuracy of the mean weight registered by the dwelling house scales to the known calibration weight tested. For punch scales just, significant differences of weights between the test load and the weight displayed on the home scales occurred for all calibration weights and both weighed researchers (p < 0.05 for all). In contrast, significant differences for digital calibration accuracy occurred only with the 75 kg calibration weight (p < 0.05). Punch scales were significantly more imprecise than digital scales at all test weights (Table 2). Figure i visually displays the absolute weight imprecision across each calibration weight test load. Scales became increasingly less precise equally weight load increased; nevertheless, imprecision as a percent of total weight exam load was inversely related to weight load. Accuracy did not vary by historic period of the scale. At that place was no pregnant deviation between dial scales ≤three years old (n = 10) and those ≥3 years old (northward = eight), and no differences between digital scales ≤3 years old (n = 25) compared to those ≥three years old n = 18). Thus, scale type, not age, is likely the source of inaccuracy and imprecision.

Figure 1
figure 1

Habitation bathroom scale weight imprecision at 6 scale weight exam loads*. *Punch n = eighteen, Digital 10 kg due north = 37; 25 kg n = 42; 50, 75, 100 kg n = 43; 110 kg northward = 41. Triangle marking and dashed line: Dial% of Weight (n = xviii). Circumvolve marker and dashed line: Digital% of Weight (northward = 35). Foursquare marker and solid line: Punch (northward = 18). Foursquare mark and dashed line: Digital (n = 35).

Full size image

Table 1 Scale accuracy: mean weights registered past scales compared to scale weight tested

Total size tabular array

Table 2 Comparison of dial and digital scale absolute value of weight imprecision at various test loads

Full size table

Multinomial regression was used to examine associations between absolute weight imprecision (i.e., <0.45 kg., 0.45 to <0.91 kg., 0.91 to <1.8 kg., 1.8 to < two.7 kg, and ≥two.seven kg.) and type of scale. The majority of scales were precise within 0.nine kg of the actual weight of the load tested, merely the extent of imprecision increased as the tested weight increased. For case, at l kg, less than 2% of all tested scales were off by at least one.8 kg; whereas the proportion rose to nearly xiv% when the 110 kg calibration weight was tested. Further, the overall imprecision of punch scales was significantly greater than that of digital scales at all weights, with nearly 17% having a precision fault of at least 2.7 kg or ane BMI unit of measurement at a exam load of 99.8 kg or greater (p < 0.05).

Give-and-take

Findings from this study indicate that home bathroom scales are consequent in the weights measured. Dial scales were significantly more imprecise than digital scales at all scale weight test loads measured with digital dwelling scale weights differing significantly at the 75 kg test load. The imprecision at the 75 kg test load likely is due to human being mistake in recording of data (e.g. incorrectly recording the weight every bit measured by the scale) during scale testing. The finding that scale precision was significantly higher at all examination loads for digital versus dial-blazon scales confirms previous reports of pregnant, positive correlations between calibration precision and accurateness [10]. Although the reasons for the differences between dial and digital scale precision are not completely clear, digital scales take fewer moving parts to get out of alignment or go damaged and have mechanisms to automatically set the starting weight to aught [9].

Although dial scales were significantly more imprecise than digital scales, absolute imprecision tended to be within 0.91 kg of calibration weights, a level far below the threshold that would cause weight to result in an error of i BMI unit (i.e., approximately 2.7 kg) [22]. It is also within the ~0.five kg fluctuation in body weight considered equally normal daily variation in healthy adults [22, 23]. For children, expected daily variation in weight is about 1.five ± 0.5% of their body weight or about 375 to 750 g for children who weigh 25 to 50 kg [twenty]. For very young children, a difference of 0.91 kg could place them in a different BMI-for-historic period percentile, potentially resulting in misclassification of their BMI [22]. The present report suggests that punch scales in particular lack accuracy at weights below x kg; thus, employ of a dial scale to counterbalance small children should exist avoided. Given that weight distribution did not affect scale accurateness, it may be feasible for parents with immature children who take dial scales to derive kid weight past subtracting their own weight from their weight while holding the kid. Hereafter research is needed to explore the accurateness and feasibility of this technique.

This study suggests that inaccuracies in cocky-reported weight probable are due in large function to human being bias and/or reporting or call up errors and not the home bathroom scales. Other studies have found that mothers with less education are more likely to provide inaccurate cocky-reported weight [5]. The majority of participants had a digital calibration, suggesting that these are more likely to be used in self-reported weight. In improver, the finding that all scales were used on hard flooring, such as tile, woods, or cement, indicates that consumers understand the upshot of floor coverings on scale accuracy, or scales are used in bathrooms, which coincidentally take hard flooring. The infrequent scale history, however, suggests that consumers could benefit from reminders to ready scales to zero before taking weights. Alternately, cocky-zeroing digital scales can help overcome this potential source of measurement error.

Conclusions

These findings suggest that errors made in self-reported weights are more probable due to human mistake or social desirability than scale inaccuracy. Importantly, this written report suggests that home bath scales, specially digital scales, provide sufficiently accurate and consistent results for apply in public health research. Providing participants with instructions for calibrating their dwelling bathroom scales before utilise may further meliorate the accurateness of cocky-reported weight. In addition, researchers can query participants about scale characteristics such as type of flooring, room in which scale is housed, presence of moisture or steam in the environment that may cause rusting (i.e. in a bathroom), participant ability to calibrate the scale, age of scale and signs of wear to help in interpretation of the data collected. Future inquiry should likewise develop and validate instructions for measuring peak at home to improve the overall accuracy of self-reported BMI. Finally, researchers should determine whether other factors, such equally socioeconomic status or participant historic period, affect the blazon of scale owned, the amount of habiliment, and the frequency with which it is calibrated.

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Acknowledgements

MY, KS, JMB, VQ and CBB received funding from the United States Department of Agronomics, National Institute of Nutrient and Agriculture, Grant Number 2011-68001-30170. VQ also received funding from the Eunice Kennedy Shriver National Institute of Child Health and Human Development Intramural Research Preparation Laurels.

Author information

Affiliations

  1. Department of Nutritional Sciences, Rutgers, The State University of New Bailiwick of jersey, 26 Nichol Avenue, Davison Hall, 08901, New Brunswick, NJ, United states of america

    Meredith Yorkin, Kim Spaccarotella, Jennifer Martin-Biggers & Carol Byrd-Bredbenner

  2. Partitioning of Intramural Population Wellness Enquiry, Eunice Kennedy Shriver National Establish of Child Health & Human Evolution, National Institutes of Health, 6100 Executive Boulevard, 20892, Bethesda, Dr., USA

    Virginia Quick

Corresponding author

Correspondence to Jennifer Martin-Biggers.

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Competing interest

The authors declare that they have no competing interests.

Authors' contributions

The following co-authors contributed to the work: MY in data collection, manuscript preparation and manuscript review. KS in manuscript preparation and manuscript review. VQ in data assay, manuscript preparation and manuscript review. JMB in data collection and manuscript review. CBB in study design and manuscript review. All authors read and approved the concluding manuscript.

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Yorkin, M., Spaccarotella, G., Martin-Biggers, J. et al. Accuracy and consistency of weights provided by home bathroom scales. BMC Public Health thirteen, 1194 (2013). https://doi.org/10.1186/1471-2458-13-1194

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Keywords

  • Trunk weight
  • Trunk mass index
  • Validity

Where Is Kg on the Baby Weight Scales

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