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Understanding Data

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The grand delusion: Why nothing is as it seems. Cookies on the New Scientist website close Our website uses cookies, which are small text files that are widely used in order to make websites work more effectively.

The grand delusion: Why nothing is as it seems

To continue using our website and consent to the use of cookies, click away from this box or click 'Close' Find out about our cookies and how to change them Log in Your login is case sensitive I have forgotten my password close My New Scientist Look for Science Jobs. NCI Cancer Bulletin for May 1, 2012. Over the past several years, the conversation about cancer screening has started to change within the medical community.

NCI Cancer Bulletin for May 1, 2012

Be it breast, prostate, or ovarian cancer, the trend is to recommend less routine screening, not more. These recommendations are based on an emerging—if counterintuitive—understanding that more screening does not necessarily translate into fewer cancer deaths and that some screening may actually do more harm than good. Much of the confusion surrounding the benefits of screening comes from interpreting the statistics that are often used to describe the results of screening studies. An improvement in survival—how long a person lives after a cancer diagnosis—among people who have undergone a cancer screening test is often taken to imply that the test saves lives.

But survival cannot be used accurately for this purpose because of several sources of bias. Sources of Bias A graphic illustrating lead-time bias. Evaluating the Literature. Recommended Texts Andersen B.

Evaluating the Literature

Methodological Errors in Medical Research. Oxford, England: Blackwell Scientific Publications; 1990. Gehlbach S. Interpreting the medical literature. Data: Uncertainty, Error, and Confidence. The Olympic sport of biathlon (Figure 1) is a cross-country ski race of 20 km in which the athletes stop on four occasions to shoot 0.57 cm diameter bullets from a .22 caliber rifle at targets.

Data: Uncertainty, Error, and Confidence

The sport requires not only great endurance, but exceptional accuracy as the athletes shoot on two occasions from the prone position (lying down) and on two occasions while standing. The targets the athletes aim for are all 50 m away, but the size varies to match the precision expected of them; those targeted while shooting in the prone position are 4.5 cm in diameter while those targeted from the more difficult standing position are 11.5 cm in diameter. In both cases, however, the diameter of the target is many times larger than the diameter of the bullet itself – why? While the legend of Robin Hood splitting one arrow with another is well-known, it is also unrealistic. Data: Analysis and Interpretation. Before you decide what to wear in the morning, you collect a variety of data: the season of the year, what the forecast says the weather is going to be like, which clothes are clean and which are dirty, and what you will be doing during the day.

Data: Analysis and Interpretation

You then analyze those data. Perhaps you think, "It's summer, so it's usually warm. " That analysis helps you determine the best course of action, and you base your apparel decision on your interpretation of the information. You might choose a t-shirt and shorts on a summer day when you know you'll be outside, but bring a sweater with you if you know you'll be in an air-conditioned building. Though this example may seem simplistic, it reflects the way scientists pursue data collection, analysis, and interpretation. Scientific data collection involves more care than you might use in a casual glance at the thermometer to see what you should wear. Data collection, analysis, and interpretation: Weather and climate. Data: Statistics. Modern science is often based on statements of statistical significance and probability.

Data: Statistics

For example: 1) studies have shown that the probability of developing lung cancer is almost 20 times greater in cigarette smokers compared to nonsmokers (ACS, 2004); 2) there is a significant likelihood of a catastrophic meteorite impact on Earth sometime in the next 200,000 years (Bland, 2005); and 3) first-born male children exhibit IQ test scores that are 2.82 points higher than second-born males, a difference that is significant at the 95% confidence level (Kristensen & Bjerkedal, 2007). But why do scientists speak in terms that seem obscure? If cigarette smoking causes lung cancer, why not simply say so?

Scientific Communication: Understanding Scientific Journals and Articles. We've all read the headlines at the supermarket checkout line: "Aliens Abduct New Jersey School Teacher" or "Quadruplets Born to 99-Year-Old Woman: Exclusive Photos Inside.

Scientific Communication: Understanding Scientific Journals and Articles

" Journals like the National Enquirer sell copies by publishing sensational headlines, and most readers believe only a fraction of what is printed. A person more interested in news than gossip could buy a publication like Time, Newsweek or Discover. These magazines publish information on current news and events, including recent scientific advances. These are not original reports of scientific research, however.

In fact, most of these stories include phrases like, "A group of scientists recently published their findings on... " Scientists publish their original research in scientific journals, which are fundamentally different from news magazines. Scientific journals vs. popular media Comprehension Checkpoint Articles published in scientific literature are considered primary literature when Reading the primary literature.