ResearchGate Q&A lets scientists and researchers exchange questions and answers relating to their research expertise, including areas such as techniques and methodologies.
Browse by research topic to find out what others in your field are discussing.
- How do I calculate statistical sampling error and confidence limits as my sample approaches the entire population?
My understanding of the statistical sampling error is derived from the binomial distribution where the variance, which is the square of the standard deviation, is simply N, the size of the sample. I believe that I know, or once knew, that the confidence limit is calculated from this distribution using an error function integral, Erf(x). In my physics career, we always worked with samples that were small compared with the whole population, and one got used to calculating the statistical component of the total error from sigma = SQRT(N). Estimating systematic errors was where most of the error analysis effort was spent.
Now I am doing social science research where one has access, on some occasions, to entire populations, for example, the number of women graduating with Electrical Engineering degrees from U.S. institutions year-by-year. When I propagate the sampling errors through a calculation of the ratio of women to women and men graduates, I get an enormous error, larger than and comparable to the ratio itself.
Clearly, I am doing something wrong. For example:
1.) Elementary calculus or algebraic errors (see attached)
2.) Violating assumption(s) of the simple propagation of errors scheme:
a.) the component errors are small compared with the measured quantities.
b.) the component errors are uncorrelated with one another.
3.) Applying sigma = SQRT(N) when I have the entire sample
4.) <strike> Something else I remain blind to. </strike> My main mistake was adding the central value to the error before graphing the main value with error bars. Merely graphing the main value with error bars works as expected. (Edit made 27 August 2014.)
For what it is worth, another physicist kindly checked (1.) and (2.) for me and said they were correct.
It seems to me that it should be possible to calculate the sampling error as the sample approaches 100% of the population and the confidence limit approaches 100%. In this case, the sampling error should approach zero, smoothly, I would imagine.
If the sampling error is simply zero when one has the entire sample, this formula should tell me. If I had this formula, and understand how to derive it, it seems that the sampling error being zero when one has the entire sample would be easier to accept.
It seems to me that there would still be systematic errors. But these are hard to estimate, particularly where self-reported data is aggregated nationwide.
It also seems to me that there may still be errors related to the population size, but I have no understanding or intuition for that, other than the fact that the data look "naked" to me without their error bars and that to the naked eye, smaller populations (e.g. astronomy) appear to have more year-to-year statistical fluctuation that larger populations (e.g. biology)
If one of you could get me back on the statistical path, I would greatly appreciate that.
The regression equations above show that the percentage of women in the fields is increasing, on average, by small amounts. (Technically, the analysis should be logit transformed. But, that makes interpreting the results even worse.)
It is also possible that these data could use some Time Series analysis too. It would be possible to create a Time Series analysis with logistic data. (I know when this comes up. I don't know who to analyze for it.)
The differences between each field are statistically significant. The coefficients in front of the 'Field' term are probabilities. So, if we look at the best field on the list, Physics, (Yes, I am biased;-) the value 0.003494 means that the percentage of women in the field grows, on average, by 0.35% per year. The percentages of women in math and computer science are lower. The percentages of the other fields are increasing faster than physics.
As far as the error bars go, I like the 95% Ci and PI. That tends to make showing differences a lot easier. Placing an error bar on each point is a bit busy or visual analysis. From the point of view of statistics and ANOVA based analysis methods, the assumption that the variability is homogeneous means those error bars should be the same size.Following
- What are the most promising experimental results on nanofluids? What are the contradictory results of nanofluids? what is the best review paper?
There are many papers published in the subject of nanofluids in theoretical and experimental papers. But, I want to focus on the experimental results. What are the contradictory results in experimental papers? What are the best review papers in the concept of nanofluids?
What are the new questions about the nanofluids?
- Native Gel Troubleshooting
I have question regarding Native gel (15%). My protein molecular weight is 13 kda and it supposed to form dimer when ligand is added.The ligand is around 500Da. When I run native gel, my protein dint enter into resolving gel.I ran it at 70 V for 7 hours in cold room and observed that my dye front ran till end,
Attached is my native gel picture. With reference to my native gel, the first 3 lanes are my protein alone. It is strucked up and not enter the resolving gel. Moreover I understand if the protein sample struck on the well, It means its getting aggregated. so the part of my protein is aggregated but rest dint enter the resolving gel.
The lane 4 -6 are the samples with protein and ligand. It supposed to form dimer when it run. But I couldnot interpret anything from the gel.
May i know how can I interpret results from native gel ? How can I check the dmerisation using native gel ? Which recipe I have to follow ?Following
- is there any helpful material and manuals for ADS software? Basics of ADS, helpful documentation, and manuals for beginners.
You can visit this youtube channel for detailed video tutorials on using ADS. you can also follow the following blog
Besides these resources there are example projects which you can access through fie>open examples menu and there are templates available in the schematic window for routine tasks . These templates can be accessed from insert>templates menu in the schematic window .Following
- What is your definition of 'environment'?
One of the popular words today is 'environment', used in quite different contexts. What is your definition?
Dear Marcel et al., like some others here, I tend to use the word as ecological environment with its biotic and abiotic components.
Besides that, other occasions when I use 'environment' are as in Bandura's theory, where Personal variables (like motivation) interact with environmental variables (like college, school, teachers, peers), and interact with Behavior variable (like satisfaction in learning sciences).Following
- How can I do a cytotoxicity test of polymeric nanoparticles loaded with cancer drug?
I have polymeric nanoparticles loaded with drug. I want to do cytotoxicity test. However, what concentration of drug, nanoparticles, polymer should I take? What will be my basis?
Sounds like a plan. I have got papers but was not sure if that woul be the best way. Thank you for your suggestion.Following
- Does anyone have experience with Gel filtration purification?
I have a question in gel filtration purification. My protein is pure after Nickel beads (I dint see any extra bands or degradation after Nickel purification). But when I run in gel filtration column I observe so many peaks of low molecular weight than my protein of interest. But when I run those extra peaks in sds gel, I couldnot see any bands.
I tried re run the eluted fraction from Gel filtration. But still I can see extra peaks of low molecular weight which is observed in gel filtration chromatogram, but when I run SDS page I couldnot observe any bands.
My SEC column is calibrated and my protein elutes at right size. So I could say that my column is in good condition
I need your kind suggestions on this extra peaks eluting. Thanks in advance
Thanks for suggestions. My FPLC measures 280nm wavelength. I tried running those low molecular peaks in SDS gel.But I coudlnt see any.
Moreover my protein dont have tryptophan residue. So my understanding is that the low molecualr weight peak is not from my protein. My column is well calibrated and hence the extra peaks are not from my column either. So wondering where the things come ?
ANother thing, I have run Native gel (15%) for these protein. Surprisignly the protein dint enter into my resolving gel. My protein molecular weight is 13 kda and it supposed to form dimer when ligand is added.
With reference to my native gel, the first 3 lanes are my protein alone. It is strucked up and not enter the resolving gel. Moreover I understand if the protein sample struck on the well, It means its getting aggregated. so the part of my protein is aggregated but rest dint enter the resolving gel,
May i know how can I interpret results from native gel ? How can I check the dmerisation using native gel ? WHich recipe I have to follow ?
I tried blue native gel recipe, But it doesnot give me any clue.Appeciate all your help.Following
- Anyone familiar with the potential causes of Chronic urticaria? Very often the cause for chronic urticaria seems unknown. The episodes of urticaria subside with a few doses of anti histamine. Even on detailed history the onset is vague, no particular time or duration. Basic investigations show normal range of blood counts. Can histamine levels be estimated in these patients?
Urticaria is still surrounded with many queries but some observations may push researchers to make more efforts to reach the possible underlying causes for such conditions serious and annoying. Malaria in endemic areas was noticed to be presented in some cases with acute urticaria and sometimes recurrent with every attack.Following
- How Accessing NTFS volume in DOS?
i can't understand this way explain it.....Following
- Samaresh Bera added an answer in DOS:How do i remove a paper that was not published and that i do not want in your database?
the paper is Adaptive time-series designs for evaluating complex multic...
we want it removed.
You can simply go to your profile => contribution =>
There are three options: publish full text, publish resources, and REMOVE.
Please click on remove button for the paper you want to remove. Your paper will be removed from your profile, and it will not be visible to anyone. I am not sure whether it will be removed from their database or not. However, I am sure that it will not be visible to anyone (including you).Following
- How do I check oligomers / dimers of the protein using Native Gel ?
I am new to protein chemistry,
Can I know how do I check oligomers / dimers of the protein using Native Gel ? Thanks in advance.
thanks for suggestions.
Can I undersand whether you mean run SDS gel with DTT and without DTT ? I did this already. But I couldnt find any differnce in the gel band.
Is there any other way apart from Gel filtration / MALS to determine dimerisation of the protein ? Thanks in advanceFollowing
- ISense with Shawn Simulator
How we can integrate iSense platform with Shawn Simulator ?Following
- Should a teacher focus on 'rigorous learning' or 'learning with entertainment'? It has been seen that many teachers in universities have become entertainers rather than focusing mainly on value-addition and learning. A lot of time gets devoted to pleasing the students; knowing them personally; building good relations with them; and telling jokes and creating humour; the focus becomes more of good feedback than rigor. Keeping the audience motivated is good for effective teaching; but since a lot of time goes in entertainment less time remains for analysis and conceptualization. What is your preference and why?
There are some students who are self initiators 9or) study out of their own interest, for such of those students, whether the teacher's style is 'rigorous' or 'entertaining' does not matter. This is mostly seen in Executive programmes or Post Graduate programmes.Following
- What could be the safety measures to handle carbon monoxide in closed lab environment ? CO is highly toxic to human, It is challenging to deal with it in syngas fermentation.
Thank you Manoj for your valuable answerFollowing
- What is the relationship between SIA (Social Impact Assessment) and SEA (Strategic Environmental Assessment) ? Dr. Bashkim Mal Lushaj: SIA is defined as an activity designed to identify and predict the impact on the biogeophysical environment and on man's health and well-being of legislative proposals, policies, programs, projects, and operational procedures, and to interpret and communicate information about the impacts and their effects(Dr. Bashkim Mal Lushaj) and SEA is a systematic decision support process, aiming to ensure that environmental and possibly other sustainability aspects are considered effectively in policy, plan and programme making. (Fischer, 2007)
Your may read the following article on social impact assessment of hydropowerdam.
In this two paper you will find EIA, SEA, SIA
However, we can conclud that SIA is a part of EIA and SEA is a concise report for higher authorities to make the final decision (nothing but shortened EIA).Following
- Isn't it true that children in poor countries must work to feed themselves and their families?
That is an image that has been portrayed and may seem acceptable to some. But the reality is that children wouldn't have to work if employers paid their parents a living wage and if governments made affordable education for all children a priority. And most child weavers are working in debt bondage, which means that they do not even earn a wage. What do you think?
Yes, Children in poor counties work to feed their parents and themselves.Following
- How to calculate actual gas production quantitatively from microbial culture in serum bottles? Water displacement value should be added with headspace volume or not?
Thank you for your answer Dr. SOLAR,
actually I wanted to know the way to calculate yield. whether displacement + headspace is accountable each time or just displacement.Following
- Should I use acetone to fix the Promoter-GUS tissue before staining buffer?
I use 90% acetone fix the tissue of promoter-GUS transgenic rice plant. The staining result turn out to be dark blue, not the bright blue like others in articles. And in some organs the GUS result was too much differnent to the qRT result. I was thinking the tissue after fixation would be true than the tissue without fixation. Now I am confusing, does the acetone fixation give me the wrong GUS singal?
I never did the fixation step before gus staining. Fresh tissue should be immersed in X-gluc solution. After the desired staining time is over, you please do the removal of chlorophyll by treating them with 70% etOH at 50°C. you can preserve it (stained tissue) for long time in 70% etOH at 4°C. I think this would help you a little bit. Best of luckFollowing
- Anyone engaged in animal face recognition?
I just start a project to do animal face recognition, does anyone know some methods to improve the recognition rate?which algorithm is best? thanks very much.Following
- Do you embed pedagogy in your LMS and if so then how do you do it? Ever since 1996, I have tried every possible thing you can imaging regarding elearning. eLearning has nothing to do with LMSs. So far, most people I know of teaching online courses run it purely as a Document Management System. At best, some used so called LMSs as Content Management Systems (CMSs). The bottom line question is: What makes a website a learning environment? What are the elements and how they relate to each other. Therefore, sharing how you put pedagogy in virtual environments may be possible (and collectively) allow us to answer those questions.
We use Embedded XL file for facilitating calculations in Compensation & Benefits Curriculum. The XL sheet is embedded on to the Power point and the PPT is either attached to an email or even web hosted (for relatively permanent period).Following
- Should we question the credibility of international conferences?
We see most of international conferences accept more than 90 percent of the papers that they receive regardless of the quality of the papers or plagiarism possibilities. Shall it make us think that the conferences are only business?
some conferences are more credible than being questioned. Some papers that are submitted in international conferences, even low level conferences are sometimes high quality papers, but generally,
Can somebody be proud of having a conference paper? Why do people put it in their CV while the registration fee only matters for most of the conferences?Following
- Any software packages suggestions for nanomaterials research?
My dear friends, I am planing to do some simulation work on nanowires/ nanomaterials growth aspects. Please suggest some soft wares (free and paid also). It is bit urgent for me.
- Where can I find a good database for GHG emission factors with the differences per country? see above
For calculate GHG emission for specific sector you can use of emission factors for each sectors and equipment regarding to type of energy consumption that Us.EPA Emissions Inventory Guidance mention it as AP-42 but for GHG inventory of each country you can refer to IPCC and UNFCCC annual reports.Following
- Can anyone provide me a source of industry level data on wages for men and women in low income countries?
I am currently writing a paper on international trade and wage inequality by skill (skilled and unskilled occupations) and gender for low income countries. I planned to use ILO data for occupational wages but found wages data for low income countries are missing in most cases. It would be helpful if I find any other source.
Please refer http://www.ilo.org/empelm/what/WCMS_114240/lang--en/index.htmFollowing
- How can we synthesize the verilog code with UPF?
Is it possible to synthesize the verilog code with UPF which contains the insertion od power domains, supply nets, retention cells and isolation cells? If it can be done, which is the tool that supports the synthesize? Also, can I perform the power analysis of this code?
You may want to read these documents -
- How do I ascertain that my isolated compound from a medicinal plant is a new compound?
Isolation from a medicinal plant that has been characterised with NMR and MS.
Can any one help me with the interpretation of spectral data (NMR/FT-IR/MS-MS) for one of my purified compound.Following
- How should I complete RT-PCR data validation?
I have done RT-PCR to check the expression level of 10 genes on human hippocampus who had mesial temporal lobe epilepsy due to hippocampal sclerosis and compared with the normal human hippocampus from the brain bank tissue repository (n=40 in each group). My RT-PCR data showed significant results in 7/10 genes. Now I want to validate the results by doing immunohistochemistry on these brain tissue samples.
My question is that in how many tissues, I should do the IHC to validate the results?
Thank you very much for your reply. I got the answer :) :) I will be doing western blot also.
Have a great day
- Is there is decrease in number of neurons with aging?
There are controversial reports about decrease in number of neurons so is it actaully happens?
For a case history that has become emblematic of how one may turnaround their AD diagnosis through hearing correction and by addressing the underlying causes of chronic disesase and dementias, I've attached the seminar notes from my "Memory for LIfe" Series Lectures.Following
- Can anyone help me to interpret NMR spectrum for powder samples?
I am working with some organic compounds synthesized by me and some purchased. I have taken NMR spectra. How to interpret that NMR spectrum of my compounds? Is there any books or reference websites available for it. Kindly give suggestions.
Before you try to interpret solid state NMR spectra you should be familiar with NMR theory, there are some books about organic structure analysis using NMR.
Nuclear Magnetic Resonance Spectroscopy (Lambert) to mention one of them.
The following link can be useful to you for solid state NMR
- Is there a complete method in the literature explain how to use iron/manganese oxide as catalyst in Biocathodes of Microbial Fuel Cell?
Thanks @Hooshyar HossiniFollowing