2009 ◽  
Vol 8 (2) ◽  
pp. 74-93
Author(s):  
SILVIA MAYÉN ◽  
CARMEN DÍAZ ◽  
CARMEN BATANERO

The focus of this research is the concept of median, which has received scarce interest in previous research. We analyse the open responses given by 518 Mexican students from Educación Secundaria (Junior) and Bachillerato (Senior) Secondary Education to a problem involving the computation of median. Using some ideas from the onto-semiotic approach, we classify the responses, taking into account the central tendency measure used, and describe the students’ semiotic conflicts. We use the chi-square test to study possible dependence between responses and students’ group. We observe better results in computation in Educación Secundaria students but better competence to select the best representative value in Bachillerato students. First published November 2009 at Statistics Education Research Journal: Archives


2013 ◽  
Author(s):  
Suhaida Abdullah ◽  
Sharipah Soaad Syed Yahaya ◽  
Abdul Rahman Othman

2015 ◽  
Vol 9 (13) ◽  
pp. 1
Author(s):  
Tobi Kingsley Ochuko ◽  
Suhaida Abdullah ◽  
Zakiyah Binti Zain ◽  
Sharipah Soaad Syed Yahaya

<p class="zhengwen"><span lang="EN-GB">This study centres on the comparison of independent group tests in terms of power, by using parametric method, such</span><span lang="EN-GB"> as the Alexander-Govern test. The Alexander-Govern (<em>AG</em>) test uses mean as its central tendency measure. It is a better alternative compared to the Welch test, the James test and the <em>ANOVA</em>, because it produces high power and gives good control of Type I error rates for a normal data under variance heterogeneity. But this test is not robust for a non-normal data. When trimmed mean was applied on the test as its central tendency measure under non-normality, the test was only robust for two group condition, but as the number of groups increased more than two groups, the test was no more robust. As a result, a highly robust estimator known as the <em>MOM</em> estimator was applied on the test, as its central tendency measure. This test is not affected by the number of groups, but could not control Type I error rates under skewed heavy tailed distribution. In this study, the Winsorized <em>MOM</em> estimator was applied in the <em>AG</em> test, as its central tendency measure. A simulation of 5,000 data sets were generated and analysed on the test, using the <em>SAS</em> package. The result of the analysis, shows that with the pairing of unbalanced sample size of (15:15:20:30) with equal variance of (1:1:1:1) and the pairing of unbalanced sample size of (15:15:20:30) with unequal variance of (1:1:1:36) with effect size index (<em>f</em> = 0.8), the <em>AGWMOM </em>test only produced a high power value of 0.9562 and 0.8336 compared to the <em>AG </em>test, the <em>AGMOM </em>test and the <em>ANOVA </em>respectively and the test is considered to be sufficient.</span></p>


2015 ◽  
Vol 9 (12) ◽  
pp. 1
Author(s):  
Tobi Kingsley Ochuko ◽  
Suhaida Abdullah ◽  
Zakiyah Binti Zain ◽  
Sharipah Syed Soaad Yahaya

This study examines the use of independent group test of comparing two or more means by using parametric method, such as the Alexander-Govern (<em>AG</em>) test. The Alexander-Govern test is used for comparing two or more groups and is a better alternative compared to the James test, the Welch test and the <em>ANOVA</em>. This test has a good control of Type I error rates and gives a high power under variance heterogeneity for a normal data, but it is not robust for non-normal data. As a result, trimmed mean was applied on the test under non-normal data for two group condition. But this test could not control the Type I error rates, when the number of groups exceed two groups. As a result, the <em>MOM</em> estimator was introduced on the test, as its central tendency measure and is not influenced by the number of groups. But this estimator fails to give a good control of Type I error rates, under skewed heavy tailed distribution. In this study, the <em>AGWMOM </em>test was applied in Alexander-Govern test as its central tendency measure. To evaluate the capacity of the test, a real life data was used. Descriptive statistics, Tests of Normality and boxplots were used to determine the normality and non-normality of the independent groups. The results show that only the group middle is not normally distributed due extreme value in the data distribution. The results from the test statistic show that the <em>AGWMOM</em> test has a smaller p-value of 0.0000002869 that is less than 0.05, compared to the <em>AG</em> test that produced a p-value of 0.06982, that is greater than 0.05. Therefore, the <em>AGWMOM</em> test is considered to be significant, compared to the <em>AG</em> test.


2019 ◽  
Vol 74 ◽  
pp. 33-40
Author(s):  
Rascius-Endrigho A.U. Belfort ◽  
Sara P.C. Treccossi ◽  
João L.F. Silva ◽  
Valdir G. Pillat ◽  
Celso B.N. Freitas ◽  
...  

2021 ◽  
Vol 38 (3) ◽  
pp. 731-738
Author(s):  
Sibghatullah I. Khan ◽  
Ganjikunta Ganesh Kumar ◽  
Pandya Vyomal Naishadkumar ◽  
Sarvade Pedda Subba Rao

Diagnosing chronic obstructive pulmonary disease (COPD) from lung sounds is time consuming, onerous, and subjective to the expertise of pulmonologists. The preliminary diagnosis of COPD is often based on adventitious lung sounds (ALS). This paper proposes to objectively analyze the lung sound signals associated with COPD. Specifically, empirical mode decomposition (EMD), a data adaptive signal decomposition technique suitable for analyzing non-stationary signals, was adopted to decompose non-stationary lung sound signals. The use of EMD on lung sound signal results in intrinsic mode functions (IMFs), which are symmetric and band limited. The analytic IMFs were then computed through the Hilbert transform, which reveals the instantaneous frequency content of each IMF. The Hilbert transformed signal is analytic, and has a complex representation containing real and imaginary parts. Next, the central tendency measure (CTM) was introduced to quantify the circular shape of the analytical IMF plot. The result was taken as a useful feature to distinguish normal lung sound signal with ALS. Simulation results show that the CTM of analytic IMFs has a strong ability to distinguish between normal lung sound signals and ALS.


2015 ◽  
Vol 53 (11) ◽  
pp. 1231-1237 ◽  
Author(s):  
Laurita dos Santos ◽  
Joaquim J. Barroso ◽  
Elbert E. N. Macau ◽  
Moacir F. de Godoy

2021 ◽  
Vol 10 (8) ◽  
pp. e14410817237
Author(s):  
Francielly V. Correa ◽  
Aline M. Diolindo Meneses ◽  
Sara P. Carvalho ◽  
Antônio P. Mendes ◽  
Laurita dos Santos

Anxiety is a negative emotional response to situations that threaten the subject. Objective: The present study aims to verify the influence of anxiety on heart rate variability, considering two specific times: hospitalization and before surgery. In this analytical and cross-sectional study, the Hospital Anxiety and Depression Scale (HADS) was used to classify anxiety levels. Methodology: The time series of RR intervals were collected by Polar® monitor. Nonlinear methods and decision tree algorithm were combined with HADS scale to analyze the influence of the preoperative period on heart rate variability. The nonlinear methods used detrended fluctuation analysis (DFA), recurrence quantification analysis (RQA), and central tendency measure (CTM). Results: Among the 42 study participants, 13 (31%) were classified as anxious at hospital admission. The applied time domain methods found an increase in the heart rate variability (HRV) values in all features analyzed (p < 0.05). CTM method showed HRV reduction for the values considering radius between 6 and 20 milliseconds (p < 0.05). Conclusion: The anxiety identified at admission is directly related to the reduction in heart rate variability demonstrated by nonlinear methods, such as the central tendency measure.


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