Statistical Methods in Assessing Agreement

Li, Lin; Hedayat, A.; Sinha, Bikas K.; Yang, Min

doi:10.1198/016214502753479392

Cited by 372 publications

(340 citation statements)

References 16 publications

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“…2). The level of overall agreement can be measured by the accuracy component C b of the concordance correlation coefficient (18). Specifically, C b lies between 0 and 1 and measures how far the best fit linear relationship between two estimates deviates from the oneto-one line.…”

Section: Resultsmentioning

confidence: 99%

Diel size distributions reveal seasonal growth dynamics of a coastal phytoplankter

Hunter-Cevera¹,

Neubert²,

Solow

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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Phytoplankton account for roughly half of global primary production; it is vital that we understand the processes that control their abundance. A key process is cell division. We have, however, been unable to estimate division rate in natural populations at the appropriate timescale (hours to days) for extended periods of time (months to years). For phytoplankton, the diel change in cell size distribution is related to division rate, which offers an avenue to obtain estimates from in situ observations. We show that a matrix population model, fit to hourly cell size distributions, accurately estimates division rates of both cultured and natural populations of Synechococcus. Application of the model to Synechococcus at the Martha's Vineyard Coastal Observatory provides an unprecedented view that reveals a distinct seasonality in division rates. This information allows us to separate the effects of growth and loss quantitatively over an entire seasonal cycle. We find that division and loss processes are tightly coupled throughout the year. The large seasonal changes in cell abundance are the result of periods of time (weeks to months) when there are small systematic differences that favor either net growth or loss. We also find that temperature plays a critical role in limiting division rate during the annual spring bloom. This approach opens a path to quantify the role of Synechococcus in ecological and biogeochemical processes in natural systems.flow cytometry | phytoplankton blooms | FlowCytobot | cyanobacteria M arine phytoplankton contribute ∼50% of global net primary production (1), mediate global biogeochemical cycles, and form the base of marine food webs. It is vital that we understand the factors that govern their abundance, even more so in light of ongoing climate change. The key to this is an understanding of the rate at which phytoplankton cells divide under different environmental conditions. Division rate cannot be measured from changes in cell abundance alone, as changes in abundance result from interactions between cell division and other processes such as predation, advection, sinking, and mixing. Further, we lack approaches that can resolve these processes on scales relevant to the cells' responses to their environment. To overcome this, estimates of abundance and division rate are needed on time scales of hours to days and extending for weeks, months, and ultimately years. Although some progress has been made with automated sampling (2), a practical method for estimating division rates across this wide range of scales has remained elusive. Conventional methods require incubations (3, 4) or sample manipulation and handling (5-7), neither of which can be feasibly conducted at daily resolution for extended duration.For the important class of picophytoplankton (≤2 μm in diameter), estimation of division rates has been attempted from in situ diel changes in cell size. During daylight, individual cells photosynthesize and increase in volume. The increase in cell volume during daylight hours provides a...

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Section: Resultsmentioning

confidence: 99%

Diel size distributions reveal seasonal growth dynamics of a coastal phytoplankter

Hunter-Cevera¹,

Neubert²,

Solow

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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“…The CCC represents the variation of the linear relationship between two variables from the 45°line of perfect agreement passing through the origin. 8,9 The CCC analysis provides a measure of precision which corresponds to the Pearson correlation coefficient, and it also delivers a measure of accuracy. The assumption of normal distribution of the differences was checked by the Shapiro-Wilk W-test for normal data.…”

Section: Needle Insertionmentioning

confidence: 99%

An ultrasound-assisted approach facilitates spinal anesthesia for total joint arthroplasty

Chin

Perlas

Singh

et al. 2009

Can J Anesth/J Can Anesth

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Purpose Spinal anesthesia can be challenging in patients undergoing total joint arthroplasty because of poorly palpable surface landmarks and age-related changes in the lumbar spine. We hypothesized that pre-procedural ultrasound imaging would be effective in identifying the lumbar intervertebral spaces and would provide an accurate measure of the depth to the intrathecal space. Methods Fifty patients undergoing elective total joint arthroplasty were recruited in this prospective descriptive study. Using a curved-array 2-5 MHz transducer, the lumbar spine was imaged in two views, i.e., longitudinal parasagittal (LP) and transverse midline (TM). The intervertebral levels were identified by counting upwards from the sacrum. The locations of the interlaminar spaces were identified by visualizing the ligamentum flavum-dura mater complex and the posterior aspect of the vertebral body. The needle insertion point for a midline approach was determined from the ultrasound examination and was marked on the skin of the patient's back. ResultsThe mean patient age was 67 ± 10 yr, and 46% of the patients had a body mass index [30 kg Á m -2 . Surface landmarks were difficult or impossible to palpate in 38% of the patients. The scan quality on the LP and TM views was adequate or better in 100 and 98% of the patients, respectively. Dural puncture was achieved with one needle insertion attempt and within two needle insertion attempts in 84% and 98% of the patients, respectively. The ultrasoundmeasured depth to the intrathecal space correlated well with the actual needle insertion depth (concordance correlation coefficient = 0.82, accuracy 0.95, precision 0.86), with a tendency to overestimate the depth by just 2.1 ± 5.4 mm. Conclusions Ultrasound imaging of the lumbar spine provides clinically useful information that can facilitate spinal anesthesia in the older orthopedic patient population.

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“…Agreement statistics require that a boundary value and CP are set to confidence limits described in Table 4. Agreement between values obtained by XRF methods (EDXRF_EMP, EDXRF_FP and EDXRF_FPML) and values measured using ICP-OES is described using agreement statistics derived by Lin (1989) and Lin et al (2002). These agreement statistics describe the proportion of data that lies within an acceptable boundary Table 4.…”

Section: Developing Empirical Calibrations For Edxrfmentioning

confidence: 99%

A rapid and multi-element method for the analysis of major nutrients in grass (Lolium perenne) using energy-dispersive X-ray fluorescence spectroscopy

Daly

Fenelon

2017

Irish Journal of Agricultural and Food Research

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Elemental analysis of grass (Lolium perenne) is essential in agriculture to ensure grass quality and animal health. Energy-dispersive X-ray fluorescence (EDXRF) spectroscopy is a rapid, multi-element alternative to current methods using acid digestion and inductively coupled plasma optical emission spectrometry (ICP-OES). Percentage phosphorus (P), potassium (K), magnesium (Mg) and calcium (Ca), determined from grass samples using EDXRF, were within 0.035, 0.319, 0.025 and 0.061, respectively, of ICP-OES values. Concordance correlation coefficients computed using agreement statistics ranged from 0.4379 to 0.9669 (values close to one indicate excellent agreement); however, the level of agreement for each element depended on the calibrations used in EDXRF. Empirical calibrations gave excellent agreement for percentage P, K and Ca, but moderate agreement for percentage Mg due to a weaker correlation between standards and intensities. Standardless calibration using the fundamental parameters (FP) approach exhibited bias, with consistently lower values reported for percentage P and Mg, when compared with ICP-OES methods. The relationship between the methods was plotted as scatter plots with the line of equality included, and although correlation coefficients indicated strong relationships, these statistics masked the effects of consistent bias in the data for percentage P and Mg. These results highlight the importance of distinguishing agreement from correlation when using statistical methods to compare methods of analysis. Agreement estimates improved when a matching library of grass samples was added to the FP method. EDXRF is a comparable alternative to conventional methods for grass analysis when samples of similar matrix type are used as empirical standards or as a matching library.

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Statistical Methods in Assessing Agreement

Cited by 372 publications

References 16 publications

Diel size distributions reveal seasonal growth dynamics of a coastal phytoplankter

Diel size distributions reveal seasonal growth dynamics of a coastal phytoplankter

An ultrasound-assisted approach facilitates spinal anesthesia for total joint arthroplasty

A rapid and multi-element method for the analysis of major nutrients in grass (Lolium perenne) using energy-dispersive X-ray fluorescence spectroscopy

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