Covariance vs. Correlation

Covariance and correlation are two statistical concepts that are closely related, both conceptually and by their name. The excerpts below are from a concise article that differentiates them.

Difference Between Covariance and Correlation

“Correlation is a special case of covariance which can be obtained when the data is standardised. Now, when it comes to making a choice, which is a better measure of the relationship between two variables, correlation is preferred over covariance, because it remains unaffected by the change in location and scale, and can also be used to make a comparison between two pairs of variables.”

Key Differences Between Covariance and Correlation

“The following points are noteworthy so far as the difference between covariance and correlation is concerned:

  1. “A measure used to indicate the extent to which two random variables change in tandem is known as covariance. A measure used to represent how strongly two random variables are related known as correlation.
  2. “Covariance is nothing but a measure of correlation. On the contrary, correlation refers to the scaled form of covariance.
  3. “The value of correlation takes place between -1 and +1. Conversely, the value of covariance lies between -∞ and +∞.
  4. “Covariance is affected by the change in scale, i.e. if all the value of one variable is multiplied by a constant and all the value of another variable are multiplied, by a similar or different constant, then the covariance is changed. As against this, correlation is not influenced by the change in scale.
  5. “Correlation is dimensionless, i.e. it is a unit-free measure of the relationship between variables. Unlike covariance, where the value is obtained by the product of the units of the two variables.”

Source

Difference Between Covariance and Correlation by Surbhi S

Invalidating Bloodletting with Science

Blood on the Tracks – Podcast Episode 38

Learn about a piece of epidemiological history: one of the earliest examples of population-level clinical studies influencing medical practice. This podcast tells the story of how French physician Pierre Charles Alexandre Louis studied a group of patients and ended up discovering quantitative evidence on the detriment of bloodletting. Learning the history helps place these tools in a broader context, which isn’t crucial, but interesting nonetheless.

Listen to the Podcast here

The first population study in history was born out of a dramatic debate involving leeches, “medical vampires,” professional rivalries, murder accusations, and, of course, bloodletting, all in the backdrop of the French Revolution. The second of a multipart series on the development of population medicine, this episode contextualizes Pierre Louis’ “numerical method,” his famous trial on bloodletting, and the birth of a new way for doctors to “know”.


Source

Bedside Rounds: Episode 38: Blood on the Tracks (PopMed #2)

Public Health in the Precision-Medicine Era

Ronald Bayer, Ph.D., and Sandro Galea, M.D., Dr.P.H.

“The NIH’s most recent Estimates of Funding for Various Research, Condition, and Disease Categories report (www.report.nih.gov/categorical_spending.aspx) shows, for example, that total support in fiscal year 2014 for research areas including the words ‘gene,’ ‘genome,’ or ‘genetic’ was about 50% greater than funding for areas including the word ‘prevention.’…The proportion of NIH-funded projects with the words ‘public’ or ‘population’ in their title, for example, has dropped by 90% over the past 10 years, according to the NIH Reporter.”

“Without minimizing the possible gains to clinical care from greater realization of precision medicine’s promise, we worry that an unstinting focus on precision medicine by trusted spokespeople for health is a mistake — and a distraction from the goal of producing a healthier population.”

Read More


Source

NEJM: Public Health in the Precision-Medicine Era by Ronald Bayer, Ph.D., and Sandro Galea, M.D., Dr.P.H.

Earthlings (2005)

Earthlings is a 2005 American documentary film about humankind’s total dependence on animals for economic purposes.  Presented in five chapters (pets, food, clothing, entertainment and scientific research) the film is narrated by Joaquin Phoenix, featuring music by Moby, and was written, produced and directed by Shaun Monson.”


How Not to Die describes the numerous health benefits of eating a plant-based diet. After reading through half the book, I watched Earthlings to see arguments from the animal rights activists for eliminating animal products from the dinner table. Personal health has always been my primary interest for minimizing meat consumption. But the message in this documentary is just as difficult to ignore as it is to watch.

There are some valid counter arguments to abandoning meat, which are listed in this reddit thread. The most compelling was that from an Indian man who argues he will not stop eating meat nor stop providing it for his family because he has genuine concern that his children my not survive due to malnutrition. Perhaps citizens of the more developed nations are the primary audience for this documentary.

I have watched a handful of anti-meat documentaries, and often they appeal to emotions such as shame, guilt, or anger. Earthlings takes a more objective role, showing film of industrial animal manufacturing in the United States. It was refreshing to be treated as a neutral observer, instead of being reprimanded. There are definite appeals to emotion, but the dialogue in the documentary is more calm than any I’ve seen before.

Earthlings has made me reconsider my current relationship with meat and animal products.  I imagine I have grown up with more livestock experience than many of my neighbors. I learned from my family to slaughter fish, chickens, turkeys, and rabbits for food. I attempted a pescatarian diet for several years in my twenties, but only for personal health reasons. This is the most cognizant I have been of my indirect participation in the massive consumption of animals, and what that actually means.


Three Stages of Truth

  1. Ridicule
  2. Violent Opposition
  3. Acceptance

Attributed to German Philosopher Arthur Schopenhauer (1788–1860)


Sources

Using It or Losing It? The Case for Data Scientists Inside Health Care

“As much as 30% of the entire world’s stored data is generated in the health care industry. A single patient typically generates close to 80 megabytes each year in imaging and electronic medical record (EMR) data. This trove of data has obvious clinical, financial, and operational value for the health care industry, and the new value pathways that such data could enable have been estimated by McKinsey to be worth more than $300 billion annually in reduced costs alone…Read More


Source

NEJM Catalyst: Using It or Losing It? The Case for Data Scientists Inside Health Care by Marco D. Huesch, MBBS, PhD & Timothy J. Mosher, MD

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