Recent developments in the design of field experiments: III. Fractional replication

1946 ◽  
Vol 36 (3) ◽  
pp. 184-191 ◽  
Author(s):  
D. J. Finney
Keyword(s):  
Statistical Analysis ◽  
Field Experiments ◽  
Block Size ◽  
Five Factors ◽  
Main Effect ◽  
Recent Developments ◽  
Four Blocks ◽  
Factor Interactions ◽  
Main Effects ◽  
Factor Interaction

When a factorial experiment involves many factors each of which is tested at two levels, economy of space and material may be effected by using only a fraction of a complete replicate of all possible combinations of levels of the factors. The consequence is that each main effect and each interaction has one or more aliases, and the experiment cannot distinguish which member of a set of aliases is responsible for an observed difference in yields. For less than five factors, this feature prevents fractional replicate designs from being much use; for five or more factors, the fraction can be so chosen that main effects and two-factor interactions have only higher order interactions as their aliases, and the possibility that these are important may often be ignored. Within the fraction of a replicate chosen for an experiment, confounding of interactions may be introduced in order to reduce the block size.Designs likely to be useful in field experiments are those for six factors in four blocks of eight, for seven factors in eight blocks of eight, and for eight factors in eight blocks of sixteen or in sixteen blocks of eight; in the first of these a two-factor interaction is amongst those confounded, but elsewhere all main effects and two-factor interactions are unconfounded. The method of construction of the blocks, for these designs and those involving more factors, has been described, and an example of the statistical analysis of experimental results (which presents no special difficulties) has been given.

Recent developments in the design of field experiments. IV. Lattice squares with split plots

1947 ◽  
Vol 37 (2) ◽  
pp. 156-162 ◽  
Author(s):  
O. Kempthorne
Keyword(s):  
Field Experiments ◽  
Factorial Designs ◽  
Split Plot ◽  
Trial Testing ◽  
Recent Developments ◽  
Factor Interaction ◽  
Three Factor

The testing of a large number of varieties or treatments can generally be most conveniently made by the use of the quasi-factorial designs devised by Yates. The value of such designs is enhanced by the possibility of introducing further treatments on parts of the plots. The present paper describes a lattice square trial testing 25 organic treatments (actually 22 different treatments with a control represented three times) in which all combinations of nitrogen, phosphate and potash were also tested by splitting the plots and confounding the three-factor interaction with whole plots, the total number of split-plots being 300. Both the design and analysis are comparatively simple and straight-forward, and will serve as an example of the use of split-plot confounding in most types of quasi-factorial designs.

Statistical Analsysis to Evaluate Heavy Metal Pollution in the Air Obatained by Moss Technique in Hanoi and its Surrounding Region

2019 ◽  
Vol 29 (3SI) ◽  
pp. 411
Author(s):  
N. H. Quyet ◽  
Le Hong Khiem ◽  
V. D. Quan ◽  
T. T. T. My ◽  
M. V. Frontasieva ◽  
...  
Keyword(s):  
Heavy Metal ◽  
Statistical Analysis ◽  
Metal Pollution ◽  
Heavy Metal Pollution ◽  
Principal Component ◽  
Multivariate Statistical ◽  
Five Factors ◽  
Heavy Metal Elements ◽  
Surrounding Areas ◽  
Potential Pollution

The aim of this paper was the application of statistical analysis including principal component analysis to evaluate heavy metal pollution obtained by moss technique in the air of Ha Noi and its surrounding areas and to evaluate potential pollution sources. The concentrations of 33 heavy metal elements in 27 samples of Barbula Indica moss in the investigated region collected in December of 2016 in the investigated area have been examined using multivariate statistical analysis. Five factors explaining 80% of the total variance were identified and their potential sources have been discussed.

Forms, Importance, and Ineffability of Factor Interactions to Define Personality Disorders: Comment on Lilienfeld et al. (2019)

2019 ◽  
Author(s):  
Stephen D Benning ◽  
Edward Smith
Keyword(s):  
Personality Disorders ◽  
False Positive Rate ◽  
Empirical Work ◽  
Design Studies ◽  
Linear Threshold ◽  
Positive Rate ◽  
Saturation Effects ◽  
Factor Interactions ◽  
Main Effects ◽  
Criterion Variables

The emergent interpersonal syndrome (EIS) approach conceptualizes personality disorders as the interaction among their constituent traits to predict important criterion variables. We detail the difficulties we have experienced finding such interactive predictors in our empirical work on psychopathy, even when using uncorrelated traits that maximize power. Rather than explaining a large absolute proportion of variance in interpersonal outcomes, EIS interactions might explain small amounts of variance relative to the main effects of each trait. Indeed, these interactions may necessitate samples of almost 1,000 observations for 80% power and a false positive rate of .05. EIS models must describe which specific traits’ interactions constitute a particular EIS, as effect sizes appear to diminish as higher-order trait interactions are analyzed. Considering whether EIS interactions are ordinal with non-crossing slopes, disordinal with crossing slopes, or entail non-linear threshold or saturation effects may help researchers design studies, sampling strategies, and analyses to model their expected effects efficiently.

Chemical effects on UV irradiation absorption of fouled quartz sleeves in ultraviolet disinfection

2008 ◽  
Vol 8 (2) ◽  
pp. 217-222 ◽  
Author(s):  
Beibei Zhu Sun ◽  
Ernest Blatchley ◽  
Mike Oliver ◽  
Cheng Zheng ◽  
Kristofer Jennings
Keyword(s):  
Statistical Analysis ◽  
Uv Disinfection ◽  
Uv Absorbance ◽  
Ultraviolet Disinfection ◽  
High Chemical ◽  
Chemical Surface ◽  
Chemical Effects ◽  
Uv Transmittance ◽  
Main Effects ◽  
Iron And Manganese

The effects of foulant chemical composition on ultraviolet (UV) absorbance of fouled quartz sleeves in UV disinfection systems were studied. Statistical analysis was conducted to examine the effects of nine fouling chemicals on the UV transmittance changes of fouled quartz lamp sleeves. The results demonstrated that the main effects were attributable to surface concentrations of iron and manganese. The surface concentrations of calcium and copper had no significant effects on the UV absorbance of fouled sleeves. The interaction effects of copper with iron and magnesium with manganese were also revealed from the statistical analysis. The model is able to give reasonable predictions of the UV absorbance characteristics of foulants from other UV systems. However, several limitations of this model were identified. First, the model does not accurately predict the absorbance at relatively high chemical surface concentrations. Second, the model does not account for the possible effects of anions and organics on UV absorption of fouled quartz sleeves.

scholarly journals Effects of kinship correction on inflation of genetic interaction statistics in commonly used mouse populations

2021 ◽  
Author(s):  
Anna L Tyler ◽  
Baha El Kassaby ◽  
Georgi Kolishovski ◽  
Jake Emerson ◽  
Ann E Wells ◽  
...  
Keyword(s):  
Mixed Model ◽  
Linear Mixed Model ◽  
Genetic Interaction ◽  
Recombinant Inbred Lines ◽  
Test Statistics ◽  
Test Statistic ◽  
Kinship Matrix ◽  
Main Effect ◽  
Main Effects ◽  
Interaction Test

Abstract It is well understood that variation in relatedness among individuals, or kinship, can lead to false genetic associations. Multiple methods have been developed to adjust for kinship while maintaining power to detect true associations. However, relatively unstudied, are the effects of kinship on genetic interaction test statistics. Here we performed a survey of kinship effects on studies of six commonly used mouse populations. We measured inflation of main effect test statistics, genetic interaction test statistics, and interaction test statistics reparametrized by the Combined Analysis of Pleiotropy and Epistasis (CAPE). We also performed linear mixed model (LMM) kinship corrections using two types of kinship matrix: an overall kinship matrix calculated from the full set of genotyped markers, and a reduced kinship matrix, which left out markers on the chromosome(s) being tested. We found that test statistic inflation varied across populations and was driven largely by linkage disequilibrium. In contrast, there was no observable inflation in the genetic interaction test statistics. CAPE statistics were inflated at a level in between that of the main effects and the interaction effects. The overall kinship matrix overcorrected the inflation of main effect statistics relative to the reduced kinship matrix. The two types of kinship matrices had similar effects on the interaction statistics and CAPE statistics, although the overall kinship matrix trended toward a more severe correction. In conclusion, we recommend using a LMM kinship correction for both main effects and genetic interactions and further recommend that the kinship matrix be calculated from a reduced set of markers in which the chromosomes being tested are omitted from the calculation. This is particularly important in populations with substantial population structure, such as recombinant inbred lines in which genomic replicates are used.

scholarly journals A Sequential Multiple Assignment Randomized Trial (SMART) study of medication and CBT sequencing in the treatment of pediatric anxiety disorders

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Bradley S. Peterson ◽  
Amy E. West ◽  
John R. Weisz ◽  
Wendy J. Mack ◽  
Michele D. Kipke ◽  
...  
Keyword(s):  
Anxiety Disorder ◽  
Anxiety Disorders ◽  
Randomized Trial ◽  
The Other ◽  
Smart Study ◽  
Main Effect ◽  
Multiple Assignment ◽  
Stage 1 ◽  
Main Effects ◽  
Treatment Sequences

Abstract Background Treatment of a child who has an anxiety disorder usually begins with the question of which treatment to start first, medication or psychotherapy. Both have strong empirical support, but few studies have compared their effectiveness head-to-head, and none has investigated what to do if the treatment tried first isn’t working well—whether to optimize the treatment already begun or to add the other treatment. Methods This is a single-blind Sequential Multiple Assignment Randomized Trial (SMART) of 24 weeks duration with two levels of randomization, one in each of two 12-week stages. In Stage 1, children will be randomized to fluoxetine or Coping Cat Cognitive Behavioral Therapy (CBT). In Stage 2, remitters will continue maintenance-level therapy with the single-modality treatment received in Stage 1. Non-remitters during the first 12 weeks of treatment will be randomized to either [1] optimization of their Stage 1 treatment, or [2] optimization of Stage 1 treatment and addition of the other intervention. After the 24-week trial, we will follow participants during open, naturalistic treatment to assess the durability of study treatment effects. Patients, 8–17 years of age who are diagnosed with an anxiety disorder, will be recruited and treated within 9 large clinical sites throughout greater Los Angeles. They will be predominantly underserved, ethnic minorities. The primary outcome measure will be the self-report score on the 41-item youth SCARED (Screen for Child Anxiety Related Disorders). An intent-to-treat analysis will compare youth randomized to fluoxetine first versus those randomized to CBT first (“Main Effect 1”). Then, among Stage 1 non-remitters, we will compare non-remitters randomized to optimization of their Stage 1 monotherapy versus non-remitters randomized to combination treatment (“Main Effect 2”). The interaction of these main effects will assess whether one of the 4 treatment sequences (CBT➔CBT; CBT➔med; med➔med; med➔CBT) in non-remitters is significantly better or worse than predicted from main effects alone. Discussion Findings from this SMART study will identify treatment sequences that optimize outcomes in ethnically diverse pediatric patients from underserved low- and middle-income households who have anxiety disorders. Trial registration This protocol, version 1.0, was registered in ClinicalTrials.gov on February 17, 2021 with Identifier: NCT04760275.

scholarly journals Effect of Frozen Storage on Polyphenol Oxidase, Antioxidant Content, and Color of Pawpaw (Asimina Triloba [L.] Dunal) Fruit Pulp

2017 ◽  
Vol 6 (3) ◽  
pp. 93 ◽  
Author(s):  
Robert G Brannan ◽  
Gai Wang
Keyword(s):  
Ascorbic Acid ◽  
Polyphenol Oxidase ◽  
Frozen Storage ◽  
Color Difference ◽  
Browning Index ◽  
Air Samples ◽  
Significant Difference ◽  
Main Effect ◽  
Effect Of Treatment ◽  
Main Effects

Polyphenol oxidase (PPO) activity values for pawpaw pulp during frozen storage were measured for the main effect of month of storage at three levels (0, 4, 8 months) and treatment at four levels (vacuum, air, ascorbic acid or n-acetylcysteine). A significant effect of treatment was observed in PPO activity (p<0.001). Post hoc analysis revealed no significant difference between samples that were vacuum packaged and those for which no attempt to exclude air was made. The addition of the two chemical browning inhibitors significantly lowered PPO activity. Ascorbic acid exhibited a significant 69% reduction in PPO activity compared to vacuum and air samples and n-acetylcysteine was significantly more effective than ascorbic acid and almost completely inhibited PPO activity compared to the vacuum and air samples. CIELAB tristimulous color values (L*, a*, b*) were used to generate the applied color values total color difference (DE), browning index, hue and chroma in pawpaw pulp for the two main effects. Analysis of variance for the main effects showed significance for all seven color attributes at p<0.001. For the main effect of storage time, ANOVA showed significance during storage for all seven color attributes at p<0.001, indicating that there were color changes during storage. Pawpaw pulp samples at 8 months of storage were significantly darker (lower L*), more yellow (higher b*), more vivid (higher chroma), and had a higher browning index than the samples at 0 or 4 months of storage. For the main effect of treatment, ascorbic acid and n-acetylcysteine treatment produced pawpaw pulp that was significantly different than samples to which air was not excluded for all seven dependent color variables. Specifically, n-acetylcysteine and ascorbic acid produced pulp that was lighter (higher L*), less red (lower a*), and more yellow (higher b* and hue), more vivid (higher chroma), and exhibited more color difference (higher DE). A strategy to inhibit enzymatic browning during frozen storage would be useful for the nascent pawpaw industry.

The Ergonomic Impact of Swype

2016 ◽  
Vol 60 (1) ◽  
pp. 1374-1378 ◽  
Author(s):  
Ibukun A. Sonaike ◽  
Tosin A. Bewaji ◽  
Paul Ritchey ◽  
S. Camille Peres
Keyword(s):  
New Technology ◽  
Touch Screen ◽  
Dynamic Activity ◽  
Extensor Muscles ◽  
Main Effect ◽  
Potential Risks ◽  
Touch Screen Devices ◽  
Study Participants ◽  
Main Effects ◽  
Biomechanical Strain

Background:Shape writing is relatively new technology for on-screen keyboards that enable users of mobile touch-screen devices to input text by drawing continuous lines. With growth of touch-screen device usage, there has risen the need to investigate potential risks that may occur during prolonged usage. Objective: The biomechanical strain on upper limb muscles were assessed while study-participants used Swype technology on a tablet touch screen device and compared with traditional/regular input methods. Methods: Study-participants performed typing tasks (email and text) using Swype and regular input methods under counterbalanced conditions with sEMG data collected to measure muscle activity during tasks. Results: Email & Text had the same exertion for all muscles except the Extensor. The interaction between task and muscle was significant, F (1.6, 27.5) = 15.39, p < .001, ηp2 = 0.48. The interaction between muscle, task and method was also significant, F (2.19, 37.19) = 3.6, p = 0.03, ηp2= 0.18. Exertion was lower for Swype but with marginal significance. Overall, Email resulted in less dynamic activity than Text with Main effects F(1, 17) = 10.07, p = 0.006, ηp2 = 0.37. Extensor has more dynamic activity than other muscles with main effect F(1.8, 29.9) = 16.51, p < 0.001, ηp2 = 0.49. Conclusion: Results indicate that Swype presents no more biomechanical strain than regular input for most muscles. Swype may result in less exertion for the Extensor muscles in the lower arm. This may be particularly true for tasks requiring interactions like those found in the email task.

Nine, Seven, Five, or Three: How Many Figures Do We Need for Assessing Body Image?

2005 ◽  
Vol 100 (2) ◽  
pp. 488-492 ◽  
Author(s):  
Neala Ambrosi-Randić ◽  
Alessandra Pokrajac-Bulian ◽  
Vladimir Takšić
Keyword(s):  
Body Image ◽  
Analysis Of Variance ◽  
Optimal Number ◽  
Female Students ◽  
Validity And Reliability ◽  
Main Effect ◽  
Dependent Variables ◽  
Post Hoc ◽  
Main Effects

320 Croatian female students ( M = 20.4 yr.) were recruited to examine the validity and reliability of figural scales using different numbers of stimuli (3, 5, 7, and 9) and different serial presentation (serial and nonserial order). A two-way analysis of variance (4 numbers × 2 orders of stimuli) was performed on ratings of current self-size and ideal size as dependent variables. Analysis indicated a significant main effect of number of stimuli. This, together with post hoc tests indicated that ratings were significantly different for a scale of three figures from scales of more figures, which in turn did not differ among themselves. Main effects of order of stimuli, as well as the interaction, were not significant. The results support the hypothesis that the optimal number of figures on a scale is seven plus (or minus) two.

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