Oct 20: Statistics in Practice

In our Briefing this week, we revisit a topic we looked at a while ago, the epidemiology of gang activity in El Salvador, and look at the impact of Covid. Our spotlight is on: Oct 30 - Nov 27:  Sample Size and Power Determination   See…

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Gangs and Covid

Dr. Carlos Carcach is Professor & Director of the Center for Public Policy at the Escuela Superior de Economía y Negocios (ESEN) in Santa Tecla, El Salvador, and coordinator of ESEN's post-graduate program in predictive analytics, which offers online instruction in partnership with Statistics.com, using…

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Clinical Trial Process that Validates Vaccines as Safe and Effective

As of this writing, there are about 40 Coronavirus vaccines in the clinical trial process, plus another 135 in preclinical development. Russia has jumped the gun and “approved” a vaccine that has just begun Phase 3 trials, and, likewise, China has approved a pre-Phase 3…

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When Probabilities Sum to More than One

In 1998, Craig Fox and Amos Tversky reported on a survey in which U.S. basketball fans were asked to judge the probability that each of 8 teams might win the championship.  Students of statistics can probably guess the outcome - the probabilities for all the…

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Density

As Covid-19 continues to spread, so will research on its behavior.  Models that rely mainly on time-series data will expand to cover relevant other predictors (covariates), and one such predictor will be gregariousness.  How to measure it?  In psychology there is the standard personality trait…

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Tracking Your Wanderings, for the Public Good

A recent development in the modeling of Covid-19 data has been the use of mobile phone location data, now available from Google, to estimate the degree to which social distancing restrictions have been implemented, and the effect they have had.   One interesting analysis comes from…

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Sensitivity and Specificity

We defined these terms already (see this blog), but how can you remember which is which, so you don’t have to look them up?  If you can remember the order in which to recite them - sensitivity then specificity, it’s easy.  Think “positive and negative”…

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COVID-19: Sensitivity, Specificity, and More

Covid-19 has brought statistical concepts and terms into the news as never before. One confusing tangle is the array of terms surrounding diagnostic test results.  The most basic is accuracy - what percent of test results are correct.  This is not necessarily the most important…

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R0 (R-nought)

For infectious diseases, R0 (R-nought) is the unimpeded replication rate of the disease pathogen in a naive (not immune) population.  An R0 of 2 means that each person with the disease infects two others.  Some things to keep in mind:    An R0 of one means…

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Coronavirus Death Toll

There are tens of thousands of epidemiologists the world over, and we are beginning to see a bumper crop of forecasts for the ultimate 2020 death toll from Covid-19.  It’s a grim but important forecasting task. Most citizens would support draconian measures to prevent deaths…

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Covid-19 Parameters

There are many moving parts in modeling the spread of an epidemic, a subject that has lately attracted the attention of great numbers of statistically-oriented non-epidemiologists (like me).  I’ve put together a “lay statistician’s guide” to some of the important parameters and factors (and I…

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Preliminary Paper

Here is a preliminary paper that suggests that RNA extraction kits, one of the main bottlenecks to Covid-19 testing in the US, can be skipped altogether and the next part of the assay (RT-qPCR) still works.  If confirmed, this result would have a major impact…

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Coronavirus – in Search of the Elusive Denominator

Anyone with internet access these days has their eyes on two constellations of data - the spread of the coronavirus, and the resulting collapse of the financial markets.  Following the 13% one-day drop of the stock market a week ago, The Wall Street Journal forecast…

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Coronavirus: To Test or Not to Test

In recent years, under the influence of statisticians, the medical profession has dialed back on screening tests.  With relatively rare conditions, widespread testing yields many false positives and doctor visits, whose collective cost can outweigh benefits.  Coronavirus advice follows this line - testing is limited…

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