Data analysis methods in optometry: is there a difference between two samples? Part 2.

In this second article, statistical ideas are extended to the problem of testing whether there is a true difference between two samples of measurements. First, it will be shown that the difference between the means of two samples comes from a population of such differences which is normally distributed. Second, the 't' distribution, one of the most important in statistics, will be applied to a test of the difference between two means using a simple data set drawn from a clinical experiment in optometry. Third, in making a t-test, a statistical judgement is made as to whether there is a significant difference between the means of two samples. Before the widespread use of statistical software, this judgement was made with reference to a statistical table. Even if such tables are not used, it is useful to understand their logical structure and how to use them. Finally, the analysis of data, which are known to depart significantly from the normal distribution, will be described.

The effect of interocular phase difference on perceived contrast

Binocular vision is traditionally treated as two processes: the fusion of similar images, and the interocular suppression of dissimilar images (e.g. binocular rivalry). Recent work has demonstrated that interocular suppression is phase-insensitive, whereas binocular summation occurs only when stimuli are in phase. But how do these processes affect our perception of binocular contrast? We measured perceived contrast using a matching paradigm for a wide range of interocular phase offsets (0–180°) and matching contrasts (2–32%). Our results revealed a complex interaction between contrast and interocular phase. At low contrasts, perceived contrast reduced monotonically with increasing phase offset, by up to a factor of 1.6. At higher contrasts the pattern was non-monotonic: perceived contrast was veridical for in-phase and antiphase conditions, and monocular presentation, but increased a little at intermediate phase angles. These findings challenge a recent model in which contrast perception is phase-invariant. The results were predicted by a binocular contrast gain control model. The model involves monocular gain controls with interocular suppression from positive and negative phase channels, followed by summation across eyes and then across space. Importantly, this model—applied to conditions with vertical disparity—has only a single (zero) disparity channel and embodies both fusion and suppression processes within a single framework.

Interferometric optical path difference measurement using sinusoidal frequency modulation of a diode laser

We describe a technique applicable to interferometric systems illuminated by a laser diode, whereby the optical path difference is recovered by means of sinusoidal modulation of the laser emission frequency.

Does the balanced scorecard make a difference to the strategy development process?

A great number of strategy tools are being taught in strategic management modules. These tools are available to managers for use in facilitating strategic decision making and enhancing the strategy development process in their organisations. A number of studies have been published examining which are the most popular tools; however there is little empirical evidence on how their utilisation influences the strategy process. This paper is based on a large scale international survey on the strategy development process, and seeks to examine the impact of a particular strategy tool, the Balanced Scorecard (BSC), upon the strategy process. Recently, it has been suggested that as a strategy tool, the BSC can influence all elements of the strategy process. The results of this study indicate that although there are significant differences in some elements of the strategy process between the organisations that have implemented the BSC and those that have not, the impact is not comprehensive.

Master and apprentice or difference and complementarity? Local government practioners, doctoral studies and co-produced research

In their search for innovative policy solutions to complex social problematics, local governance practitioners will look to synergising specific policy guidance from government departments with conceptual scientific research outputs. UK academics are also now expected to emphasise the relevance of their research and to increase its utilisation by practitioners. Away from utilitarian pressures, academics from applied discipline, such as Public Administration and Local Government Studies are increasingly drawn to the benefits of co-produced research. Despite the pressure for more co-research there are few opportunities for practitioners and academics to nurture relationships that would support close collaboration. This paper looks at the opportunity for closer collaboration when practitioners undertake research degrees, in order to enhance their cognitive skills and develop greater scientific knowledge of particular policy domains. If this route to closer collaboration is to succeed, it will require academics to think differently about their relationship with practitioner-students.

Adolescent-parent disagreement on health-related quality of life of food-allergic adolescents:who makes the difference?

Background: Food-allergic adolescents are at highest risk for food allergy fatalities, which may be partly due to compromised self-management behavior. Such behavior may be negatively influenced by conflictual situations caused by adolescent–parent disagreement on the adolescent’s health-related quality of life (HRQL). Comparisons of adolescent-self-reported and parent-proxy-reported HRQL of food-allergic adolescents have never extensively been studied. The aims of this study were to investigate disagreement in adolescent-self-reports and parent-proxy-reports on the HRQL of food-allergic adolescents and to investigate the factors influencing adolescent–parent disagreement. Methods: Teenager Form (TF) and Parent Form (PFA) of the Food Allergy Quality of Life Questionnaire (FAQLQ), Food Allergy Independent Measure (FAIM), and Brief-Illness Perception Questionnaire (Brief-IPQ) were sent to food-allergic Dutch adolescents (13–17 years) and their parents. ICCs, t-tests, and Bland–Altman plots were used to investigate adolescent–parent disagreement. Participant characteristics, illness expectations, and illness perceptions influencing adolescent–parent disagreement were studied using regression analysis. Results: Seventy adolescent–parent pairs were included. There were a moderate correlation (ICC = 0.61, P < 0.001) and no significant difference (3.78 vs 3.56, P = 0.103) between adolescent-self-reported and parent-proxy-reported HRQL at group level. However, Bland–Altman plots showed relevant differences (exceeding the minimal important difference) for 63% of all adolescent–parent pairs. Adolescent’s age (>15 years), poorer adolescent-reported illness comprehension (Brief-IPQ-TF, coherence), and higher adolescent-reported perceived disease severity (Food Allergy Independent Measure-Teenager Form & -Parent Form) were associated with adolescent–parent disagreement. Conclusions: Adolescent–parent disagreement on the adolescent’s HRQL was mainly associated with adolescents’ rather than parents’ perceptions and characteristics. Illness comprehension of the adolescent may be an important target for intervention aimed at reducing adolescent–parent disagreement.

Bridging difference - national and organisational adaptation for responsible performance

This special issue draws together a selection of articles built around a theme of bridging difference. We argue that the effective transfer of learning across boundaries is crucial in enabling the dissemination of good, and ethical, HR practice. How that transfer might occur, with respect both to the mechanisms to enable or inhibit transfer and to the nature of learning that underpins that transfer, provides the focus of what is discussed here. This is framed against a concern for the nature and future of HRM, in particular its role in ensuring responsible organisational performance. © 2013 Taylor & Francis.

Elevated left and reduced right orbitomedial prefrontal fractional anisotropy in adults with bipolar disorder revealed by tract-based spatial statistics

Context - Diffusion tensor imaging (DTI) studies in adults with bipolar disorder (BD) indicate altered white matter (WM) in the orbitomedial prefrontal cortex (OMPFC), potentially underlying abnormal prefrontal corticolimbic connectivity and mood dysregulation in BD. Objective - To use tract-based spatial statistics (TBSS) to examine WM skeleton (ie, the most compact whole-brain WM) in subjects with BD vs healthy control subjects. Design - Cross-sectional, case-control, whole-brain DTI using TBSS. Setting - University research institute. Participants - Fifty-six individuals, 31 having a DSM-IV diagnosis of BD type I (mean age, 35.9 years [age range, 24-52 years]) and 25 controls (mean age, 29.5 years [age range, 19-52 years]). Main Outcome Measures - Fractional anisotropy (FA) longitudinal and radial diffusivities in subjects with BD vs controls (covarying for age) and their relationships with clinical and demographic variables. Results - Subjects with BD vs controls had significantly greater FA (t > 3.0, P = .05 corrected) in the left uncinate fasciculus (reduced radial diffusivity distally and increased longitudinal diffusivity centrally), left optic radiation (increased longitudinal diffusivity), and right anterothalamic radiation (no significant diffusivity change). Subjects with BD vs controls had significantly reduced FA (t > 3.0, P = .05 corrected) in the right uncinate fasciculus (greater radial diffusivity). Among subjects with BD, significant negative correlations (P < .01) were found between age and FA in bilateral uncinate fasciculi and in the right anterothalamic radiation, as well as between medication load and FA in the left optic radiation. Decreased FA (P < .01) was observed in the left optic radiation and in the right anterothalamic radiation among subjects with BD taking vs those not taking mood stabilizers, as well as in the left optic radiation among depressed vs remitted subjects with BD. Subjects having BD with vs without lifetime alcohol or other drug abuse had significantly decreased FA in the left uncinate fasciculus. Conclusions - To our knowledge, this is the first study to use TBSS to examine WM in subjects with BD. Subjects with BD vs controls showed greater WM FA in the left OMPFC that diminished with age and with alcohol or other drug abuse, as well as reduced WM FA in the right OMPFC. Mood stabilizers and depressed episode reduced WM FA in left-sided sensory visual processing regions among subjects with BD. Abnormal right vs left asymmetry in FA in OMPFC WM among subjects with BD, likely reflecting increased proportions of left-sided longitudinally aligned and right-sided obliquely aligned myelinated fibers, may represent a biologic mechanism for mood dysregulation in BD.

Multimodal spectral control of a quantum-dot diode laser for THz difference frequency generation

Generation of stable dual and/or multiple longitudinal modes emitted from a single quantum dot (QD) laser diode (LD) over a broad wavelength range by using volume Bragg gratings (VBG's) in an external cavity setup is reported. The LD operates in both the ground and excited states and the gratings give a dual-mode separation around each emission peak of 5 nm, which is suitable as a continuous wave (CW) optical pump signal for a terahertz (THz) photomixer device. The setup also generates dual modes around both 1180m and 1260 nm simultaneously, giving four simultaneous narrow linewidth modes comprising two simultaneous difference frequency pump signals. (C) 2011 American Institute of Physics.

Direct observation of R...R distances in rare-earth (R) phosphate glasses by magnetic difference neutron diffraction

A magnetic difference neutron diffraction study of a rare-earth (Tb) phosphate glass has revealed exclusively the Tb...Tb distances. The difference between data taken with and without an applied magnetic field of 4 T shows Tb...Tb pairwise atomic correlations at 3.9 and 6.4 A, respectively, with relative coordination numbers of 1:14. The first distance arises when two Tb3+ ions share a common oxygen neighbor, and indicates a clustering of rare-earth ions. The second distance arises when two Tb3+ ions are coordinated to different oxygens in the same PO4 group, in a near-linear arrangement.