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  • Which type of covariate analysis one should perform if dependent variable is not normally distributed?

    I have gene expression data (dependent variable) for 4 population groups (group as fixed/categorical variable) but this data is not normally distributed. I want determine if age/BMI () can affect the statistical significance within groups.

    Which type of covariate analysis should be performed for not normally distributed data? I am not sure if covariate analysis is performed only for normally distributed data.

    If anyone knows please reply me. Thanks in advance!

    Artemis Llamosi · Paris Diderot University

    Usually, the choice of method not depends as much on normality of the data that on the expected type of relationship.

    Correlation is computed usually with Pearson's formulation (linear relationship) or Spearman formulation (monotonical relationship). For non linear, non monotonical relationships, it is problem specific. When you have enough variables and conditions, you can use things ike ANOVA or Friedman tests...

    At last, when you want to derive p-values on statistics (like is the mean of a group smaller than the mean of another) but your distributions are not typical, you may want to use bootstrapping.

  • Morteza Shabanzadeh added an answer in Circuits:
    Circuit breaker interrupts the circuit under what conditions?

    Circuit breaker interrupts the circuit under what conditions?

    Morteza Shabanzadeh · Tarbiat Modares University

    Dear Majid,

    A Circuit Breaker (C.B.) detects power system faults and protects its equipment from

    1) Overload

    2) Short circuit

    It is different from the fuse because the fuse has to be replaced after its operation but Circuit Breaker is only reset either manually or automatically.

    I hope this information is helpful for your research.


    Morteza Shabanzadeh


  • Ramezan Sahebi added an answer in Zno Thin Films:
    Is it possible to calculate wavelength dependent refractive index of ZnO thin film if i have transmiitance and absorption cofficienet values ?

    Is it possible to calculate wavelength dependent refractive index of ZnO thin film if i have transmittance and absorption coefficient values ?

    Ramezan Sahebi · Ferdowsi University Of Mashhad

    you must have absorbance and transmittance spectra of your sample.
    absorption coefficient (alpha)= 2.303 A/d
    A is absorbance and (d) is the thickness of your thin films
    you must calculate the reflectance using following equation
    alpha=-1/d Ln(T/(1-R)*2)
    the extinction coefficient (k) is given by
    k= (alpha*landa)/(4Pi)
    landa is wavelength and Pi=3.14
    then you can find the refractive index(n) using this equation
    R=[(n-1)**2 + k**2]/[(n+1)**2 + k**2]

  • Moslem Zarei asked a question in Low-Voltage:
    Hi-standard voltage is 220 volts or 230?

    Hi-standard voltage is 220 volts or 230 voltsin low voltage network? What is the minimum and maximum voltage that could be? Please respond with a valid source Thank you.

  • How can I cary out bivariate (or multivariate) normality test?

    I have a set of variables and I want to test their bivariate ot multivariate normal distribution, but I didn't know how! I want a method in excel or a statistical software such as Minitab or SPSS or SAS.

    Abdolghani Abdollahimohammad · Zabol University Of Medical Sciences

    It depends on the test you use. I suppose you are running a GLM univariate test in spss. 1. Select the predictive value and residuals under SAVE option. 2. run a scatter plot under the Graph test with the residuals score and the predictive value.

  • Kamal Eddin Bani-Hani added an answer in DAD:
    How to maintain or improve the teenagers’ relations with their fathers?

    Dear Professors/RG members/friends,

    In India most of the teen agers, when they join the colleges they stop talking to their fathers freely. They mostly approach the father through their mothers. This leads to the psychological depression of the fathers and since they don’t know how to correct this problem, behaves very strictly with their sons/daughters worsening the situation still more.
    Fathering a little son/daughter who wants nothing so much as to be "just like my dad" is much easier than fathering an adolescent son/daughter who wants to follow his/she own agenda and be his/her own man/woman.

    Dr. Shanmugasudnaram P

    Kamal Eddin Bani-Hani · Hashemite University

    Be her/his friend and father, not only a father. Contact them and talk to them in a friendly way always and show them that you LOVE them

  • Cecile Furstenberg asked a question in Euthanasia:
    When does Dignity of human being begin and end? What does this notion implies (human rights)? Is dignity specific to human?

    Can you refer to Dignity to justify the contradiccion of abortion or euthanasia? 

  • Aly Elhefni added an answer in Air Conditioning:
    For air dehumidification , which of cooling coils and chilled water spray is better and more efficient ?

    For an office building air conditioning system, if chilled water will be used . For the purpose of cooling and de-humidification, which is better and more efficient: a cooling coil or a chilled water spray?

    Aly Elhefni · Alexandria University

    Dear Dr. Maddali VS Murali ,

    Why is the cooling coil more efficient that chilled water spray ? I thought that in chilled water spray case , the heat transfer process gets more efficient since now water and air are in direct contact and the heat transfer area is much larger (boundaries of each droplet) .  

    As for change in moisture content , I believe that as far as the sprayed water temperature is lower than the dew point temperature of air , then , there is no reason that prevents the air from de-humidification . Do you agree with that ?

  • Kasım Kiraci added an answer in Aviation:
    Can anyone suggest a topic related to the the development of aviation carriers and the associated impacts on local tourism in Turkey?
    I would like to find a specialized topic for my thesis work. I would also like the topic to focus on cooperation between Greece and Turkey in the fields of tourism and aviation.
    Kasım Kiraci · Anadolu University

    The Evolution of Turkish Air Transport Industry: Significant Developments and the Impacts of 1983 Liberalization... in this article you can find the aviation development in Turkey, but it is hard to find article which you research about..

  • Mohsen Mousivand asked a question in Flac:
    How to draw longitudinal profile in FLAC 3D ( example: ydisplacement)?

    Draw Longitudinal profile

  • How do I plot a graph of concentration effect curve?

    This is a pharmacology subject where we collect some data analysis and we plot them on a graph to see the dose response curve. There is a file attachment where we add results

    There this image which my lecturer explained to draw with the data we obtained

    Dragan Pavlovic · Dalhousie University, Halifax, Canada; European University, Belgrade, Serbia.


    The people who gave you the advices obviously never did such experiments.
    Federica gave you the best advice. You also have free explanations on GraphPad site

    You will need this book if you continue with such experiments:


    You must find somebody in your surroundings to help you. It is impossible to explain it all here. Good luck.

  • Blazej Niewiadosmki added an answer in Trees:
    When a tree looses its leaves and stems following a cyclonic whether, will the tree survive and give back new shoots?

    A recent cyclone has nearly wiped out the greenery of a city. many trees are denuded and standing without any leaves. will these trees survive and get back the leaves? Are there any methods to save a tree or make it grow faster. How will the tree survive if there is no photosynthesis?

    Blazej Niewiadosmki · Adelphi University

    Look into using herbal salves to cover the wounds.

    If the bark (skin/dermal layer) of the tree is intact it should have a good chance to recover, here in the city i have observed trees cut down, leaving only the stump and new shoots did grow!!!

  • Hudson Couto do Amparo asked a question in Fruit:
    Which reference can I use to validate CCP for Patulin in apple juice?

    FDA has as critical limit for CCP chemical Patulin a declaration, from each truck supplier, with a signed information that the fruit were picked from the tree, not fallen fruit. Which investigation about can I use to validate the CCP?

  • What role does teaching about culture have in teaching a foreign language?

    In the past, teaching about native speaker culture was challenging for teachers who had never lived in that culture. Today we know that learning English is not only about interacting with native speakers, but also interacting with anyone with whom you do not share a mother tongue. 

    How important is learning about culture? Which culture(s)?

    Ana M Pérez-cabello · Universidad de Sevilla

    I feel that when teaching we should reconsider the scope. I mean it implies teaching not only the langaue but also the literature and the culture that condition that language. As said above,Technology can help, anyway. A few days ago, I was trying to make my students aware of this. For example, how can you explain idioms such as "An apple a day keeps the doctor away" (and this is not difficult to understand) or "Esta es la calor del membrillo" to non native. Lovely weekend (que te lo pases pipa -young slang-)!

  • If any coordinates will do in General Relativity, is spatial curvature necessary? Is GR more complex than necessary, and is curvature verified?

    GR was introduced along with the principle that not only is no coordinate system preferred, but that any arbitrary coordinate system would do.  The complex mathematical machinery of covariance was introduced (including tensors) to express the laws of physics, any of the laws not just GR, in arbitrary coordinates.  This allows coordinate systems in which the distances vary with position and orientation, and in which the speed of light is non-isotropic (varies by direction), and such coordinates are routinely used in famous solutions such as Schwarzschild.

    So, it is not just the curvature of Riemannian geometry that requires complexity, but most of it is required by independence from coordinates.  And if indeed physics is independent of coordinates, can coordinates be found for solving GR problems in which space (if not spacetime) is flat and therefore graspable to the ordinary intuition?

    For an introduction to analysis of orbits using only time dilation, not  spatial curvature, see paper linked below.  GR was derived from the equivalence principle on the assumption that curvature was the only way to explain equivalence, but this is an argument not a proof according to GR verification authority Cliff Will.  If another method is available, it becomes a weak argument.  Is there empirical proof of curvature?

    Charles Francis · Jesus College, Cambridge


    You say: "I don't like "length contraction" because it does not convey the full picture. I don't like "distortion of maps" because it is not obvious how it relates to any existing literature. "

    This seems like a problem with existing modern literature. Actually historically the whole study of curved geometry arose from the distortion of maps which Gauss was using in his job in cartography, at a time when improved mapping of the world was a major interest to trading nations. It still is the core idea in the mathematical definition of a manifold. We still define charts and atlases as the way to describe a manifold. I guess the problem is that this is now only presented in mathematical treatments in a way only comprehensible to mathematicians. 

    The measurables you are talking of changing, light delay and counts of metre sticks, are non-local. Locally, they don't change - lightspeed is locally constant and the definition of the metre is everywhere the same. The thing which is different and which causes the Shapiro delay is not the measurable, but the shape of the geometry. We can talk of a distortion of the geometry from flat, but not of a distortion of the measurable quantity.

  • Soon Sin Chai added an answer in Structural Geology:
    Are there any reference book/journal/papers that are related to the stability of slope cuts for melange formation?

    I am looking for analysis methods that could be carry out to analyze slope cuts in melange. The melange formation is made up of sedimentary rock blocks surrounded by mud matrix. Methods I have in hands now are X-ray diffraction, hydrometer method, Atterberg limit method and observation towards slope angle and its vegetation. I want to know is there any other methods that can be used to improve the analysis.

    Soon Sin Chai · University of Malaya

    Thanks Brendan and Ridel for the suggestions.

  • Kamal Eddin Bani-Hani added an answer in Lipids:
    What is the relationship between absorption of drugs and their lipid: water partition coefficient?

    Absorption of drugs depend on many factors one of them which is lipid: water partition coefficient, what is relation between them?

    Kamal Eddin Bani-Hani · Hashemite University

    Drug absorption is determined by the drug's physicochemical properties, formulation, and route of administration.

    In the physical sciences, a partition-coefficient (logP) or distribution-coefficient (logD) is the ratio of concentrations of a compound in a mixture of two immiscible phases at equilibrium. These coefficients are a measure of the difference in solubility of the compound in these two phases.

    Please see:


  • What is the biggest scientific coincidence that you know?
    For me the two more important are:

    1. The phase transition liquid-solid for the water is that the solid state is less dense.
    2. The dielectric screening in metals is such that the Coulomb interaction among the electrons falls at a distance of the Bohr radius.

    The first one has many important applications as the one of allowing the live in rivers during winter or so on. On the other hand, there are also very interesting electric and thermodynamic phase transitions for this material

    The second, thanks to have a so local electric interaction it allows to have almost free electrons at quite high electronic density in matter and therefore to apply theories so useful as the bands in solids. Over all in metals
    Robin Spivey · Bangor University

    Dear Daniel, some of the coincidences I've described on this thread aren't touched on in the paper (due mainly to the widespread reporting restrictions and suppression of debate in modern science). Nevertheless, these coincidences were an extremely important part of the thought processes that over the course of many months eventually led me to investigate the internal heating of planets by neutrino annihilation (it took a couple of days to be satisfied that other dark matter candidates were ruled out).

    I see the magnetic properties of iron, cobalt and nickel as important for regulating the formation of consistently sized planets. The Earth has a magnetosphere that offers a useful defence against high energy charged particles of the solar wind. In contrast, Mars, a planet with a very similar rotation rate, lost its magnetosphere 4 billion years ago and has suffered significant atmospheric ablation. Earth's magnetic field has much more to do with convection within the iron core than with ferromagnetism - especially as the core is much hotter than the Curie temperature. I don't think that ferromagnetism in iron will have much bearing on neutrino annihilation rates - but there might be some interesting things going on there which I've so far failed to spot.

    Since hydrogen has only one electron, the electrons in metallic hydrogen are degenerate, much like a white dwarf. That is the main reason why we would not expect the interiors of gas giants to be much good at mediating neutrino annihilation.

    According to the results of the analysis, we could be inhabitants of a universe capable of sustaining aquatic life over the long term with an energetic efficiency of around 99%. Actually, as energy is not destroyed, it's better to think in terms of entropy. Neutrinos carry biologically useful energy but long wavelength photons do not. You're absolutely right that the whole model rests on assessing the opportunities for neutrino annihilation and quantifying the power they can deliver. Without that it's impossible to infer anything novel about dark matter, dark energy, the existence of intelligent extraterrestrial life, the various natural coincidences or the possibility that the cosmos is endowed with purpose.

    There's a need to independently confirm (or refute) these findings but the electron-mediated annihilation of low energy neutrinos is a two-stage process that is tough to analyse. However, as the standard model has been around for decades, and particle colliders have attracted huge public investment, perhaps someone has by now tried to automate the calculation of interactions in a computer programme. For all I know, software of this kind might even be publicly accessible - but I have failed to locate anything of this kind.

  • Presentation of Data - What do you show on boxplots?


    I am writing my thesis results section and wanted some advice on presentation of data.

    Would it be appropriate to use IQR (25-75) as the box, 1.5*95% CI (outliers) as the whiskers, with both mean and median lines, to highlight the lack of normality in some continuous data sets? In the text, I give mean/95%CI for normally distributed data, and median/IQR for non-normal/non-continuous data.

    I have plotted each data set as I have reported (i.e. only showing mean or median line), but am wondering whether what I outlined above would also be an appropriate approach.

    Help much appreciated!

    Abdolghani Abdollahimohammad · Zabol University Of Medical Sciences

    I prefer the Shapiro-Wilk Test of Normality to show whether the distribution of data are normal. This test is more accurate. 

  • Can you suggest user friendly MITE identification software?


    I am trying to identify MITE sequences in sequence fragments (of 5000-10000 bp) from  wheat. Can you suggest a user friendly software ?

    Thank you


    Matej Lexa · Masaryk University

    What Nayem suggests is one of the three basic principles to look for repetitive sequences. I think you can use Repeat Masker as a tool apart of BLAST. The second approach would be to look for repetitive sequences de novo, (e.g RAP https://www.researchgate.net/publication/8339363_RAP_a_new_computer_program_for_de_novo_identification_of_repeated_sequences_in_whole_genomes) . The third approach is to look for repetitive sequences based on their structure. There are such programs for LTR TEs, but maybe this approach is not applicable to MITEs.

  • Iftikhar Ahmad asked a question in Protein Modeling:
    Has any one tell me how protein modeling software could be downloaded ?

    how that software works

  • Anil Chauhan added an answer in Cooling:
    Why is radiation pressure force non-conservative?

    Due to the non-conservative nature of radiation pressure force, it can be used for the cooling of atomic motion.

    Anil Chauhan · Indian Institute of Technology Ropar

    @Muhammad Anwar

    Thanks Dear

    As you said interaction seems to be conservative, I don't think so.we know that in cavity we have consist of one totally reflected mirror and one partial mirror and due to continuous reflection of light inside the cavity, the radiation pressure force will displace mirror a little bit or a little bit of oscillation(due to Doppler effect). so the radiation pressure force is non conservative due to the little friction force arise there. consequently we will have some thermal noise etc or dissipation. In my case, i am giving input of laser light to the cavity. that's what i was asking.



  • Can anybody suggest how to represent a limited integration equation that has many terms of Bessel functions in MATLAB?

    Hi everybody,

    I have attached an integration equation as a function of Bessel functions. The upper limit of integration is (infinite) and the lower limit is (zero). In fact, I solved it by MATLAB, but I got weird results when I just change the lower limit from zero to 0.1 or 2 and keep the upper limit as it (some value) and one more thing is that the MAXIMUM upper limit that I can reach is 10^9, beyond that amount gives me a ZERO for the whole integration!

    So I think those weird results come from the existing of the variable X^5 in the denominator of the integrand and I might not use the right command of integration to integrate like this equation as a function of Bessel functions. If there is any way to represent like this integration with those Bessel terms in MATLAB, please let me know, and I will be really appreciated that help!


    Mohammed Abdulkhabeer · Missouri University of Science and Technology

    Thank you so much Alain for your note.

  • Are PISA scores a good test for national education?

    The Programme for International Student Assessment (PISA) is a challenge to test education systems by testing the skills and knowledge of 15-year-old students.

    Do you think that this method is a good test?

    In the link you can reed the PISA 2012 results.

    Artur Banaszak · Wyzsza Szkola Gospodarki Euroregionalnej w Jozefowie

    First of all, the educational system in certain countries are so different, therefore it is hard to compare them. Also, the choice of tasting group can be seen as a problem.
    But, what is the most interesting to me, is that PISA tests results do not corresponded with the scores from our national tests. My country – Poland is located on the quite high place. The national reports say that we achieved success. After information about the PISA results, many people in Poland announced success. Aa an example might be a quote from one of the most important Polish newspapers - Gazeta Wyborcza: “We have reason to be proud and satisfied. Our youths are the most talented in the world. About that my generation could only dream of - said Prime Minister Donald Tusk” (Gazeta Wyborcza from 03.12.2013). The 2012 scores are better than ones from last years and give us a place in top of the UE.
    But, there so many voices that young people in Poland have big problem with the mathematics skills and with the understanding of written texts. Last year, about 30% students did not pass the high school graduation exams. To pass these exams is necessary to go to university or college. It seems that good score on PISA test of Polish students and the reality not always go together.
    In addition, the practice shows that the situation with Polish students is not very good. Many people working in school say that the level of knowledge and level of different skills is going down.
    Now, we can ask the question about where is the problem. I mean – are the groups for PISA test are chosen inappropriately. Or maybe, the PISA tests are too easy? Or maybe, our national exams are too demanding or too difficult .
    I do not know the answer to these questions – but we should thing of them and try to find the answer

  • Robert Mugo asked a question in Stock Exchange:
    Is it possible to undertake a test on financial contagion in only one stock market?

    if financial contagion tests can be conducted in one stock exchange, how can this be done?

  • What is the importance of Nernst Equilibrium Potential practically?

    What is the importance of Nernst Equilibrium Potential practically? especially when you do patch clamp experiments.