Data Collection

Data collection

Data  Collection 1

Data collection in the prenatal phase included physical examinations, questionnaires, foetal ultrasound examinations and biological samples. In addition, more detailed assessments are conducted in a subgroup of 1232 pregnant women and their children. At the age of 5 years, all children were invited to visit the Generation R research centre for detailed assessments. This was repeated at the age of 9 years.

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Survey data collection

With the application of probability sampling in the 1930s, surveys became a standard tool for empirical research in social sciences, marketing, and official statistics. The methods involved in survey data collection are any of a number of ways in which data can be collected for a statistical survey. These are methods that are used to collect information from a sample of individuals in a systematic way. First there was the change from traditional paper-and-pencil interviewing (PAPI) to computer-assisted interviewing (CAI). Now, face-to-face surveys (CAPI), telephone surveys (CATI), and mail surveys (CASI, CSAQ) are increasingly replaced by web surveys.

Data  Collection 2

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Sampling Big Data for Machine Learning [closed]

I believe there are still clear situations where sampling is appropriate, within and without the "big data" world, but the nature of big data will certainly change our approach to sampling, and we will use more datasets that are nearly complete representations of the underlying population.On sampling: Depending on the circumstances it will almost always be clear if sampling is an appropriate thing to do. Sampling is not an inherently beneficial activity; it is just what we do because we need to make tradeoffs on the cost of implementing data collection. We are trying to characterize populations and need to select the appropriate method for gathering and analyzing data about the population. Sampling makes sense when the marginal cost of a method of data collection or data processing is high. Trying to reach 100% of the population is not a good use of resources in that case, because you are often better off addressing things like non-response bias than making tiny improvements in the random sampling error. How is big data different? "Big data" addresses many of the same questions we've had for ages, but what is "new" is that the data collection happens off an existing, computer-mediated process, so the marginal cost of collecting data is essentially zero. This dramatically reduces our need for sampling.When will we still use sampling? If your "big data" population is the right population for the problem, then you will only employ sampling in a few cases: the need to run separate experimental groups, or if the sheer volume of data is too large to capture and process (many of us can handle millions of rows of data with ease nowadays, so the boundary here is getting further and further out). If it seems like I am dismissing your question, it's probably because I've rarely encountered situations where the volume of the data was a concern in either the collection or processing stages, although I know many haveThe situation that seems hard to me is when your "big data" population does not perfectly represent your target population, so the tradeoffs are more apples to oranges. Say you are a regional transportation planner, and Google has offered to give you access to its Android GPS navigation logs to help you. While the dataset would no doubt be interesting to use, the population would probably be systematically biased against the low-income, the public-transportation users, and the elderly. In such a situation, traditional travel diaries sent to a random household sample, although costlier and smaller in number, could still be the superior method of data collection. But, this is not simply a question of "sampling vs. big data", it's a question of which population combined with the relevant data collection and analysis methods you can apply to that population will best meet your needs.

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What is wrong in the data collection programs by the NSA and United States? How does it affect the life of a common man?

It is not about whether you have something to hide or not. The main reason why it is wrong is because it is a violation of the Fourth Amendment, which guarantees our protection against illegal search and seizures (violation of privacy). The Government is overstepping its boundaries, and acting in a way in which it is not authorized . This is a dangerous precedent to set.This is made even more dangerous by the fact that the word "terrorist" is very poorly defined. If the government is able to spy on American citizens, it could conceivably persecute people for expressing opinions (for example if someone voices support for a terrorist act). This might sound like a stretch, but something very similar to this happened in the 1950's with the word "Communist" replacing "Terrorist", and it is not inconceivable that this could happen again. (this is known as McCarthyism; here are a few links to wikipedia pages that can get you started looking into this piece of history if you are interested: McCarthyism Joseph McCarthy House Un-American Activities Committee Hollywood blacklistPeople take for granted that the government is inherently good/moral, but this is not the case. Our system of Government is, in my opinion, very good/moral, but not necessarily the people running the government. When injustices are carried out by our leaders, the American people are empowered to make changes. By spying on its citizens, the American government is threatening one of the tenants that allow us to make these changes should we need to (and when the government is directly violating the constitution, I would assert that we most certainly do need to make changes). Its not a matter of whether or not you have something to hide, its about keeping the government in check, and protecting our civil liberties; there is no guarantee that the leaders of our country will always behave in our best interests (although they may or may not mean well), unless we make sure that they do. Thats why we have the system of Checks and Balances, and the Bill of Rights, which are vital to preserving the American way of life.On a final note, keep in mind that the goal of terrorism is to spread fear. If we allow the threat posed by terrorists to scare us to the point that we sacrifice our constitution, then we are allowing them to do so, we are, if you will, allowing them to "win". Keep in mind that the United States Government was warned about the Tsarnaev brothers and the 9/11 attacks, and that this information was not sufficient to stop these people from carrying out attacks, making the effectiveness of spying on American citizens questionable. The proposition of the government setting a precedent of violating our constitutional rights is to me, much more worrisome than any sort of terrorist attack.

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