Category Archives: History of research

Filtered vs. Unfiltered: What do these terms mean?

Are we talking cigarettes?  water? coffee? other?   Yes, other.   In this case about what is sometimes called “filtered” or “unfiltered” literature in the evidence-based medicine pyramid of research evidence.  (I have more than one issue with this particular pyramid as a representation of all evidence, but for right now let’s look at filtered information & unfiltered information.  Pyramid source:  Wikimedia Commons  
Filtered Unfiltered jpg

Filtered is considered stronger–meaning that we can be more confident that literature from this category better  supports cause and effect.  I agree.

Unfiltered evidence (usually single studies etc) is considered weaker–meaning that we must be more cautious about its accuracy in representing reality.  I agree.

But, “Is unfiltered information really unfiltered?”  No filtering at all? My qualified answer is, “No.”   Argue with me if you like.

My opinion: If the “unfiltered” article is a primary source, research study that has strong design and is published in a peer-review journal then it has been filtered by multiple, expert peer reviewers just to make it to publication.

Thus, when discussing filtered vs. unfiltered one should be very clear on what those terms mean and do not mean.

Critical Thinking: When filtered literature (systematic reviews & critically appraised topics & articles) has been filtered by one individual, is that superior to unfiltered literature in terms of introducing bias?  What if the “filtered” evidence is 7 years old and a primary, “unfiltered” source(s) from this year has different findings?   What is the relationship between “filtered” and “unfiltered”–after all the “unfiltered” is the pyramid base so what does that mean?

For more Info:  For peer review, the lower level filtering of single studies, consider its 1)  advantages (  and 2) its potential flaws (


Nightingale: Avante garde in meaningful data

In honor of Nurse Week, I offer this tribute to the avante garde research work of Florence Nightingale in the Crimea that saved lives and set a precedent worth following.

Nightingale was a “passionate statistician” knowing that outcome data are convincing when one wants to change the world.  She did not merely collect the data, but also documented it in a way that revealed its critical meaning for care.

As noted by John H. Lienhard (1998-2002): Nightingale coxcombchart“Once you see Nightingale’s graph, the terrible picture is clear. The Russians were a minor enemy. The real enemies were cholera, typhus, and dysentery. Once the military looked at that eloquent graph, the modern army hospital system was inevitable.  You and I are shown graphs every day. Some are honest; many are misleading….So you and I could use a Florence Nightingale today, as we drown in more undifferentiated data than anyone could’ve imagined during the Crimean War.” (Source: Leinhard, 1998-2002)

As McDonald (2001) writes in the BMJ free, full-text,  Nightingale was “a systemic thinker and a “passionate statistician.”  She insisted on improving care by making policy & care decisions based on “the best available government statistics and expertise, and the collection of new material where the existing stock was inadequate.”(p.68)

Moreover, her display of the data brought its message home through visual clarity!

Thus while Nightingale adhered to some well-accepted, but mistaken, scientific theories of the time (e.g., miasma) her work was superb and scientific in the best sense of the word.   We could all learn from Florence.

CRITICAL THINKING:   What issue in your own practice could be solved by more data?  How could you collect that data?   If you have data already, how can you display it so that it it meaningful to others and “brings the point home”?