STA 210 – Intro to Statistical Reasoning
Chapter 1: Human Interference
8/23/23
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Inference
o a conclusion reached based on evidence and reasoning
o this reasoning process – from the known to the unknown – is more commonly what the
word inference is used to refer to and not to the set of mathematical tools that
statisticians have developed to facilitate that process in a particular way
o EXAMPLE: a politician looking at the poll results from a sample may decide on whether
they have a chance in the fall election with all voters
 Percentage of 1500 voters sampled that supported x can infer the percentage of
all voters who support x
Human Interference
o the reflexive inferences we make when we consume simple statistical constructs such as:
charts, graphs, tables, and numerical summaries
o how we naturally organize these types of information, our own interpretations of the data
o validity of our reflexive human inferences can be easily compromised (e.g., bias, careless
interpretation)
o one goal is to recognize and avoid common issues: deceptive graphs, decimal points that
are overlooked or placed incorrectly, percentages, rates, incorrect calculations
EXAMPLE: Deceptive Graphs
o Tara Parker-Pope makes the case that teenagers are more
conservative than their parents were with the following graph.
o Fact-Checking the Human Interference
 The fraction of high-school seniors who reported they
had recently consumed alcohol fell from 72% in 1980
to 40% in 2011
 Actual Change:
 The fraction of 1980 seniors who reported they had
recently consumed alcohol is illustrated as the big 128ounce jug. 2010 consumption is illustrated as the 8-ounce glass
 Suggested Change: using an actual bar graph for accessibility, starting
the scale at 0%, assuming the viewer doesn’t perceive the jug as “big”
EXAMPLE: Decimal Error
o Medication dosages have caused multiple errors
o ISMP has received reports of dosing errors, due to professionals using trailing zeros,
such as 1.0mg being read as 10mg by a pharmacist.
EXAMPLE: Percentages, Rates, and Incorrect Calculations
o The data was included in the Journal of Experimental Medicine
o It lists 6 sets of 20 animals each, with the percentages of
successful outcomes for each set.
o Why are they wrong?
 100/5=20, each increment should be in 5’s, not
random numbers