Date post: 2017-11-08 06:57
A confidence interval (CI) expresses the precision of an estimate and is often presented alongside the results of a study (usually the 95% confidence interval). The CI shows the range within which we are confident that the true result from a population will lie 95% of the time. The narrower the interval, the more precise the estimate. There is bound to be some uncertainty in estimates because studies are conducted on samples and not entire populations.
A control group (of cells, individuals or centres, for example) serves as a basis of comparison in a study. In this group, no experimental stimulus is received.
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Twin studies rely on comparing the phenotypes (observable physical traits) of monozygotic (genetically identical) twins and dizygotic (non-identical) twin pairs. The difference in correlation between phenotypes in the identical twins and the correlation in phenotypes in the non-identical twins estimate the genetic contribution to variations in phenotype (the within-twin correlation).
The test subjects were shown images of letters and numbers at the same time and instructed what to focus on. When they were told to pay attention to numbers, they had to determine if the digits were even or odd. When told to concentrate on letters, they had to say whether they were vowels or consonants.
The science of ice melt rates is advancing so fast, scientists have generally been reluctant to put a number to what is essentially an unpredictable, nonlinear response of ice sheets to a steadily warming ocean. With Hansen&rsquo s new study, that changes in a dramatic way. One of the study&rsquo s co-authors is Eric Rignot, whose own study last year found that glacial melt from West Antarctica now appears to be &ldquo unstoppable.&rdquo Chris Mooney, writing for Mother Jones , called that study a &ldquo holy shit&rdquo moment for the climate.
This study identifies a group of people and follows them over a period of time to see how their exposures affect their outcomes. This type of study is normally used to look at the effect of suspected risk factors that cannot be controlled experimentally, for example the effect of smoking on lung cancer.
These studies also test how the drug behaves in the body, examining how it is absorbed, where it is distributed, how it leaves the body and how long it takes to do this.
An experiment is any study in which the conditions are under the direct control of the researcher. This usually involves giving a group of people an intervention that would not have occurred naturally. Experiments are often used to test the effects of a treatment in people and usually involve comparison with a group who do not get the treatment.