scholarly journals Easy methods for extracting individual regression slopes: Comparing SPSS, R, and Excel

2013 ◽  
Vol 9 (2) ◽  
pp. 72-78 ◽  
Author(s):  
Roland Pfister ◽  
Katharina Schwarz ◽  
Robyn Carson ◽  
Markus Jancyzk
Keyword(s):  
Regression Slopes

Motor Subcircuits Mediating the Control of Movement Velocity: A PET Study

1998 ◽  
Vol 80 (4) ◽  
pp. 2162-2176 ◽  
Author(s):  
Robert S. Turner ◽  
Scott T. Grafton ◽  
John R. Votaw ◽  
Mahlon R. Delong ◽  
John M. Hoffman
Keyword(s):  
Motor Control ◽  
Basal Ganglia ◽  
Right Hemisphere ◽  
Movement Velocity ◽  
Rate Effects ◽  
Regression Slopes ◽  
The Right ◽  
Parietal Cortices ◽  
Linear Contrasts ◽  
Rate Of Movement

Turner, Robert S., Scott T. Grafton, John R. Votaw, Mahlon R. DeLong, and John M. Hoffman. Motor subcircuits mediating the control of movement velocity: a PET study. J. Neurophysiol. 80: 2162–2176, 1998. The influence of changes in the mean velocity of movement on regional cerebral blood flow (rCBF) was studied using positron emission tomography (PET) in nine healthy right-handed adults while they performed a smooth pursuit visuomanual tracking task. Images of relative rCBF were obtained while subjects moved a hand-held joystick to track the movement of a target at three different rates of a sinusoidal displacement (0.1, 0.4, and 0.7 Hz). Significant changes in rCBF between task conditions were detected using analysis of variance and weighted linear contrasts. The kinematics of arm and eye movements indicated that subjects performed tasks in a similar manner, particularly during the faster two tracking conditions. Significant increases in rCBF during arm movement (relative to an eye tracking only control condition) were detected in a widespread network of areas known for their involvement in motor control. The activated areas included primary sensorimotor (M1S1), dorsal and mesial premotor, and dorsal parietal cortices in the left hemisphere and to a lesser extent the sensorimotor and superior parietal cortices in the right hemisphere. Subcortically, activations were found in the left putamen, globus pallidus (GP), and thalamus, in the right basal ganglia, and in the right anterior cerebellum. Within the cerebral volume activated with movement, three areas had changes in rCBF that correlated positively with the rate of movement: left M1S1, left GP, and right anterior cerebellum. No movement-related sites had rCBF that correlated negatively with the rate of movement. Regressions of mean percent change (MPC) in rCBF onto mean hand velocity yielded two nonoverlapping subpopulations of movement-related loci, the three sites with significant rate effects and regression slopes steeper than 0.17 MPC⋅cm−1⋅s−1 and all other sites with nonsignificant rate effects and regression slopes below 0.1 MPC⋅cm−1⋅s−1. Moreover, the effects of movement per se and of movement velocity varied in magnitude independently. These results confirm previous reports that movement-related activations of M1S1 and cerebellum are sensitive to movement frequency or some covarying parameter of movement. The activation of GP with increasing movement velocity, not described in previous functional-imaging studies, supports the hypothesis that the basal ganglia motor circuit may be involved preferentially in controlling or monitoring the scale and/or dynamics of arm movements. The remaining areas that were activated equally for all movement rates may be involved in controlling higher level aspects of motor control that are independent of movement dynamics.

scholarly journals How do I know what my theory predicts

2019 ◽  
Author(s):  
Zoltan Dienes
Keyword(s):  
Mediation Analysis ◽  
Null Hypothesis ◽  
Prior Information ◽  
Bayes Factor ◽  
Total Effect ◽  
Ways Of Thinking ◽  
Regression Slopes ◽  
Mean Differences ◽  
Simple Heuristics

To get evidence for or against a theory relative to the null hypothesis, one needs to know what the theory predicts. The amount of evidence can then be quantified by a Bayes factor. Specifying what one's theory predicts may not come naturally, but I show some ways of thinking about the problem, some simple heuristics that are often useful when one has little relevant prior information. These heuristics include the room-to-move heuristic (for comparing mean differences), the ratio-of-scales heuristic (for regression slopes), the ratio-of-means heuristic (for regression slopes), the basic effect heuristic (for ANOVA effects), and the total effect heuristic (for mediation analysis).

scholarly journals Revisiting the Relationships between Fat-to-Protein Ratio in Milk and Energy Balance in Dairy Cows of Different Parities, and at Different Stages of Lactation

Animals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 3256
Author(s):  
Edward H. Cabezas-Garcia ◽  
Alan W. Gordon ◽  
Finbar J. Mulligan ◽  
Conrad P. Ferris
Keyword(s):  
Energy Balance ◽  
Dairy Cows ◽  
Milk Fat ◽  
Early Lactation ◽  
Protein Ratio ◽  
Linear Relationships ◽  
Holstein Friesian ◽  
Partial Correlations ◽  
Regression Slopes ◽  
Beta Hydroxybutyrate

A statistical re-assessment of aggregated individual cow data was conducted to examine trends in fat-to-protein ratio in milk (FPR), and relationships between FPR and energy balance (EB, MJ of ME/day) in Holstein-Friesian dairy cows of different parities, and at different stages of lactation. The data were collected from 27 long-term production trials conducted between 1996 and 2016 at the Agri-Food and Biosciences Institute (AFBI) in Hillsborough, Northern Ireland. In total, 1321 lactations (1 to 20 weeks in milk; WIM), derived from 840 individual cows fed mainly grass silage-based diets, were included in the analysis. The energy balance was calculated daily and then averaged weekly for statistical analyses. Data were further split in 4 wk. intervals, namely, 1–4, 5–8, 9–12, 13–16, and 17–20 WIM, and both partial correlations and linear regressions (mixed models) established between the mean FPR and EB during these periods. Three FPR score categories (‘Low’ FPR, <1.0; ‘Normal’ FPR, 1.0–1.5; ‘High’ FPR, >1.5) were adopted and the performance and EB indicators within each category were compared. As expected, multiparous cows experienced a greater negative EB compared to primiparous cows, due to their higher milk production relative to DMI. Relatively minor differences in milk fat and protein content resulted in large differences in FPR curves. Second lactation cows displayed the lowest weekly FPR, and this trend was aligned with smaller BW losses and lower concentrations of non-esterified fatty acids (NEFA) until at least 8 WIM. Partial correlations between FPR and EB were negative, and ‘greatest’ in early lactation (1–4 WIM; r = −0.38 on average), and gradually decreased as lactation progressed across all parities (17–20 WIM; r = −0.14 on average). With increasing parity, daily EB values tended to become more negative per unit of FPR. In primiparous cows, regression slopes between FPR and EB differed between 1–4 and 5–8 WIM (−54.6 vs. −47.5 MJ of ME/day), while differences in second lactation cows tended towards significance (−57.2 vs. −64.4 MJ of ME/day). Irrespective of the lactation number, after 9–12 WIM, there was a consistent trend for the slope of the linear relationships between FPR and EB to decrease as lactation progressed, with this likely reflecting the decreasing milk nutrient demands of the growing calf. The incidence of ‘High’ FPR scores was greatest during 1–4 WIM, and decreased as lactation progressed. ‘High’ FPR scores were associated with increased energy-corrected milk (ECM) yields across all parities and stages of lactation, and with smaller BW gains and increasing concentrations (log transformed) of blood metabolites (non-esterified fatty acid, NEFA; beta-hydroxybutyrate, BHB) until 8 WIM. Results from the present study highlight the strong relationships between FPR in milk, physiological changes, and EB profiles during early lactation. However, while FPR can provide an indication of EB at a herd level, the large cow-to-cow variation indicates that FPR cannot be used as a robust indicator of EB at an individual cow level.

scholarly journals INVESTIGATING THE EFFECT OF SELF-REGULATED STRATEGY DEVELOPMENT ON TERTIARY EFL STUDENTS’ WRITING SKILLS

EDULANGUE ◽  
2019 ◽  
Vol 2 (1) ◽  
pp. 19-35
Author(s):  
Kasyfur Rahman ◽  
Imansyah Imansyah ◽  
I Made Permadi Utama
Keyword(s):  
Relative Effect ◽  
Analysis Of Covariance ◽  
Strategy Development ◽  
Control Group ◽  
Significant Difference ◽  
Writing Course ◽  
Efl Students ◽  
Regression Slopes ◽  
And Control ◽  
Writing Scores

This study aimed to investigate the relative effect of Self-Regulated Strategy Development (SRSD) teaching approach on tertiary EFL students’ writing. During two months, sixty EFL University students enrolling in basic writing course took part in this project and were divided into experimental and control groups. Pre- and post-tests were carried out to garner the intended data pertinent to the students’ writing scores. A mixed-design ANOVA was carried out to analyze the changes of writing scores of the respective groups since the assumption of homogeneity of regression slopes for the planned Analysis of Covariance was not met. The statistical evidence showed that there was a significant difference between the two groups in terms of writing scores at the significant value sig .00 < .05. The data also suggested that students who were taught using SRSD relatively outperformed their counterparts in the control group. The empirical evidence demonstrates that the use of SRSD as an instructional approach to some extent positively affects EFL students’ writing skill.

Measurement of carbamazepine and its epoxide metabolite by high-performance liquid chromatography, and a comparison of assay techniques for the analysis of carbamazepine.

1977 ◽  
Vol 23 (12) ◽  
pp. 2283-2287 ◽  
Author(s):  
G W Mihaly ◽  
J A Phillips ◽  
W J Louis ◽  
F J Vajda
Keyword(s):  
High Performance Liquid Chromatography ◽  
Liquid Chromatography ◽  
High Performance ◽  
Plasma Concentrations ◽  
Correlation Coefficients ◽  
High Performance Liquid Chromatographic ◽  
Biologically Active ◽  
Gas Liquid Chromatography ◽  
Carbamazepine Therapy ◽  
Regression Slopes

Abstract We describe a modified high-performance liquid-chromatographic method for the simultaneous analysis of carbamazepine andits biologically active metabolite, carbamazepine-10, 11-epoxide. Concentrations of both these compounds in the plasma of 35 epileptic patients receiving chronic carbamazepine therapy are presented. Concentrations of carbamazepine in plasma were related to those of carbamazepine-10, 11-epoxide (r - 0.495, P less than 0.05). Total daily doses of carbamazepine were better correlated with plasma concentrations of carbamazepine-10, 11-epoxide (r = 0.714, P less than 0.001) than of carbamazepine (r = 0.269, P greater than 0.05). Close correlations were found between results of the three assay procedures we used to measure plasma carbamazepine concentrations: high-performance liquid chromatography, gas-liquid chromatography, and enzyme immunoassay. Correlation coefficients exceeded 0.97 and regression slopes were near unity, indicating that all three procedures were individually specific for the quantification of plasma carbamazepine.

scholarly journals Description of a formaldehyde retrieval algorithm for the Geostationary Environment Monitoring Spectrometer (GEMS)

2019 ◽  
Vol 12 (7) ◽  
pp. 3551-3571 ◽  
Author(s):  
Hyeong-Ahn Kwon ◽  
Rokjin J. Park ◽  
Gonzalo González Abad ◽  
Kelly Chance ◽  
Thomas P. Kurosu ◽  
...  
Keyword(s):  
Optical Absorption ◽  
Absorption Spectroscopy ◽  
Cross Sections ◽  
Correlation Coefficients ◽  
Optical Absorption Spectroscopy ◽  
Retrieval Algorithm ◽  
Environment Monitoring ◽  
Ozone Monitoring Instrument ◽  
Nonlinear Fitting ◽  
Regression Slopes

Abstract. We describe a formaldehyde (HCHO) retrieval algorithm for the Geostationary Environment Monitoring Spectrometer (GEMS) that will be launched by the Korean Ministry of Environment in 2019. The algorithm comprises three steps: preprocesses, radiance fitting, and postprocesses. The preprocesses include a wavelength calibration, as well as interpolation and convolution of absorption cross sections; radiance fitting is conducted using a nonlinear fitting method referred to as basic optical absorption spectroscopy (BOAS); and postprocesses include air mass factor calculations and bias corrections. In this study, several sensitivity tests are conducted to examine the retrieval uncertainties using the GEMS HCHO algorithm. We evaluate the algorithm with the Ozone Monitoring Instrument (OMI) Level 1B irradiance/radiance data by comparing our retrieved HCHO column densities with OMI HCHO products of the Smithsonian Astrophysical Observatory (OMHCHO) and of the Quality Assurance for Essential Climate Variables project (OMI QA4ECV). Results show that OMI HCHO slant columns retrieved using the GEMS algorithm are in good agreement with OMHCHO, with correlation coefficients of 0.77–0.91 and regression slopes of 0.94–1.04 for March, June, September, and December 2005. Spatial distributions of HCHO slant columns from the GEMS algorithm are consistent with the OMI QA4ECV products, but relatively poorer correlation coefficients of 0.52–0.76 are found compared to those against the OMHCHO products. Also, we compare the satellite results with ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) observations. OMI GEMS HCHO vertical columns are 9 %–25 % lower than those of MAX-DOAS at Haute-Provence Observatory (OHP) in France, Bremen in Germany, and Xianghe in China. We find that the OMI GEMS retrievals have less bias than the OMHCHO and OMI QA4ECV products at OHP and Bremen in comparison with MAX-DOAS.

Twelve-Hour Urine Collection Can Be Utilized to Estimate 24-Hour Total Urinary Nitrogen in Critically Trauma Patients

2019 ◽  
Vol 152 (Supplement_1) ◽  
pp. S1-S1
Author(s):  
Hsuan-Chieh Liao ◽  
Grant O’Keefe ◽  
Fred Woo ◽  
Lisa Lawrence ◽  
Geoffrey Baird
Keyword(s):  
Correlation Coefficients ◽  
Urine Samples ◽  
Trauma Patients ◽  
Urine Collection ◽  
Sample Collection ◽  
Icu Patients ◽  
Nitrogen Levels ◽  
Significant Difference ◽  
Regression Slopes ◽  
Urinary Nitrogen

Abstract Patients suffering from trauma, burns, and sepsis are frequently in a hypermetabolic state, and as the majority of urinary nitrogen comes from amino acid metabolism, the determination of total urinary nitrogen (TUN) provides an accurate measurement of all nitrogen excreted in urine and can be used as an indicator of catabolic stress. To evaluate whether time of collection influences the performance of TUN test, 12-hour urine specimens were collected from ICU trauma patients and the 12-hour results were correlated with results from 24-hour collections. Two consecutive 12-hour urine samples were collected (06:00-18:00 hours and 18:00-06:00 hours) from surgical ICU patients. Total urinary nitrogen levels were measured in each 12-hour sample, as well as in a pooled sample (24 hours). Pyrochemiluminescence was used to determine TUN level on an Antek 9000N elemental analyzer. In this approach, the urine sample is completely oxidized at high temperature in a quartz pyrotube. Nitrogen is converted to nitric oxide (·NO), then mixed with O3 (ozone) to form nitrogen dioxide (NO2). Light is emitted and specific wavelengths between 650 and 900 nm were measured in a photomultiplier tube. The measured chemiluminescent emission is specific and proportional to the amount of nitrogen in the sample. Fifty 12-hour urine samples from 16 patients were collected. One patient was excluded from the study due to acute renal injury during the collection period. There was no significant observed circadian effect on measured TUN. The 12-hour TUN (g/total volume) was multiplied by 2 to compare to 24-hour TUN for statistical analysis. There was strong correlation between either day or night 12-hour TUN and corresponding pooled 24-hour TUN, with correlation coefficients ranging from 0.93 to 0.98 and regression slopes ranging from 0.98 to 1.01. No statistically significant difference was found between the 12-hour TUN and 24-hour TUN approaches. A 12-hour TUN collection was overall highly predictive of 24-hour TUN collection and has the advantage of convenience of sample collection and improved clinical efficiency. Serial 12-hour urine collection is therefore preferred for monitoring nitrogen balance and adjusting protein intake for critically ill ICU patients.

Polyclonal Antibody-Based ELISA and HPLC Methods for the Determination of Fumonisins in Corn: A Comparative Study

1996 ◽  
Vol 59 (8) ◽  
pp. 893-897 ◽  
Author(s):  
ERIC W. SYDENHAM ◽  
SONJA STOCKENSTRÖM ◽  
PIETER G. THIEL ◽  
JOHN P. RHEEDER ◽  
M. BRUNO DOKO ◽  
...  
Keyword(s):  
Comparative Study ◽  
Polyclonal Antibody ◽  
High Performance ◽  
Linear Regression Analysis ◽  
Correlation Coefficients ◽  
Hplc Method ◽  
Enzyme Linked Immunosorbent Assay ◽  
Regression Slopes ◽  
The Individual ◽  
The Comparative Study

The performance of an experimental polyclonal antibody (PAb)-based competitive direct enzyme-linked immunosorbent assay (CD-ELISA) developed for the analysis of fumonisins in corn was assessed by comparison with an established high-performance liquid chromatography (HPLC) method. The comparative study was conducted using a series of 20 corn samples naturally contaminated with combined fumonisin levels ranging from &lt;0.05 to &gt;5 μg/g (ppm). Linear regression analysis between the results generated by HPLC and CD-ELISA provided correlation coefficients (r) and regression slopes (b) of r = 0.960, b = 1.493 (P &lt; 0.001); r = 0.865, b = 3.903 (P &lt; 0.001); and r = 0.832, b = 0.107 (P &lt; 0.001) for the individual fumonisins B1 (FB1), B2 (FB2) and B3 (FB3), respectively, while corresponding values of r = 0.967, b = 1.059 (P &lt; 0.001) were obtained for the combined FB1, FB2, and FB3 concentrations. In 3 of 18 fumonisin-positive corn samples, combined fumonisin levels determined by CD-ELISA were between 85 and 100% higher than those determined in the same extracts by HPLC, while in 13 other samples, CD-ELISA results were between 1.8 and 53% higher than those determined by HPLC. Conversely, in 2 of 18 samples, CD-ELISA results were lower than those determined by HPLC. The differences recorded between HPLC and the experimental PAb-based CD-ELISA were far less than those previously recorded for other mono- and polyclonal antibody-based CD-ELISA systems. The results indicate that the experimental PAb-based CD-ELISA may be effectively applied for the initial screening for fumonisins in corn.

Incorrect least-squares regression coefficients in method-comparison analysis.

1979 ◽  
Vol 25 (3) ◽  
pp. 432-438 ◽  
Author(s):  
P J Cornbleet ◽  
N Gochman
Keyword(s):  
Standard Deviation ◽  
Least Squares ◽  
Least Squares Method ◽  
Regression Line ◽  
Method Comparison ◽  
Regression Coefficients ◽  
Least Squares Regression ◽  
Data Set ◽  
Data Points ◽  
Regression Slopes

Abstract The least-squares method is frequently used to calculate the slope and intercept of the best line through a set of data points. However, least-squares regression slopes and intercepts may be incorrect if the underlying assumptions of the least-squares model are not met. Two factors in particular that may result in incorrect least-squares regression coefficients are: (a) imprecision in the measurement of the independent (x-axis) variable and (b) inclusion of outliers in the data analysis. We compared the methods of Deming, Mandel, and Bartlett in estimating the known slope of a regression line when the independent variable is measured with imprecision, and found the method of Deming to be the most useful. Significant error in the least-squares slope estimation occurs when the ratio of the standard deviation of measurement of a single x value to the standard deviation of the x-data set exceeds 0.2. Errors in the least-squares coefficients attributable to outliers can be avoided by eliminating data points whose vertical distance from the regression line exceed four times the standard error the estimate.

scholarly journals Evaluation of Sentinel-3A Wave Height Observations Near the Coast of Southwest England

2019 ◽  
Vol 11 (24) ◽  
pp. 2998 ◽  
Author(s):  
Francesco Nencioli ◽  
Graham D. Quartly
Keyword(s):  
Root Mean Square Error ◽  
Mean Square Error ◽  
Root Mean Square ◽  
Wave Height ◽  
Significant Wave Height ◽  
Mean Square ◽  
Significant Wave ◽  
In Situ Observations ◽  
Regression Slopes

Due to the smaller ground footprint and higher spatial resolution of the Synthetic Aperture Radar (SAR) mode, altimeter observations from the Sentinel-3 satellites are expected to be overall more accurate in coastal areas than conventional nadir altimetry. The performance of Sentinel-3A in the coastal region of southwest England was assessed by comparing SAR mode observations of significant wave height against those of Pseudo Low Resolution Mode (PLRM). Sentinel-3A observations were evaluated against in-situ observations from a network of 17 coastal wave buoys, which provided continuous time-series of hourly values of significant wave height, period and direction. As the buoys are evenly distributed along the coast of southwest England, they are representative of a broad range of morphological configurations and swell conditions against which to assess Sentinel-3 SAR observations. The analysis indicates that SAR observations outperform PLRM within 15 km from the coast. Within that region, regression slopes between SAR and buoy observations are close to the 1:1 relation, and the average root mean square error between the two is 0.46 ± 0.14 m. On the other hand, regression slopes for PLRM observations rapidly deviate from the 1:1 relation, while the average root mean square error increases to 0.84 ± 0.45 m. The analysis did not identify any dependence of the bias between SAR and in-situ observation on the swell period or direction. The validation is based on a synergistic approach which combines satellite and in-situ observations with innovative use of numerical wave model output to help inform the choice of comparison regions. Such an approach could be successfully applied in future studies to assess the performance of SAR observations over other combinations of coastal regions and altimeters.

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