# STA 210 Lecture Notes - Lecture 3: Read All About It (Song), Numeracy, Decimal Mark

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9 Sep 2019

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~ Statistics Lecture #3 ~

Literacy and Human Inference

09/03/19

o Read All About It: BN 1.1 and 1.4

o Focused on human inference from statistical summaries

o Basic numeracy is required to asses integrity of the summaries

o Focused on:

▪ Decimal point errors

▪ Deceptive charts

▪ Competence with fractions and rates

▪ Usefulness of common benchmarks

o Inductive Inference

o The process of reasoning from the known to the unknown

o Math is more about “deductive inference.”

o A politician looking at the poll results (sample) and deciding whether she has a change in the

fall election (all voters)

o Human Inference

o An off-hand phrase taken in here to mean “inferences we make from statistical constructs

like charts, graphs, numerical summaries.”

o Think of it as how you operationalize statistical descriptions.

o Really? A College Topic?

o From an article by Ryan McCready, August 10, 2017

▪ “In this post-truth era, graphs, charts, and tables are being used to skew data or

ideas like never before.”

▪ “Misleading graphs or charts are perfect for inserting an incorrect idea into a

narrative. And that idea can spread around the world in seconds before the truth

can even get its pants on.”

▪ “All it takes is a single graph from a less than reputable source, blasted out to a list of

followers, to change a story worldwide.”

o 5 Ways Writers Use Misleading Graphs to Manipulate You

o Omitting the Baseline

▪ In most cases, the baseline for a graph is 0.

▪ But writers can skew how data is perceived by making the baseline a difference

number.

▪ This is known as a “truncated graph.”

o Manipulating the Y-Axis

▪ Expanding or compressing the scale on a graph can make changes in data seem

more or less significant than they actually are.

o Cherry Picking Data

▪ Writers may only include certain data points on their graphs to reinforce their

narratives.

▪ This can create a false impression of the data.

o Using the Wrong Graph

▪ The type of graph you use should depend on the type of data you want to visualize.

▪ Using the wrong type of graph can skew the data.

▪ Writers will sometimes use the wrong type of graph on purpose.

o Going Against Conventions

▪ Over time, we have developed standards for how data is visualizes.

▪ Flipping those conventions can make a graph confusing or misleading to readers.

o Advice from Journalist Craig Silverman

o First, journalists need to acquire the basic math skills needed to properly handle numbers

and figures.

o Second, they need to develop the habit of double-checking every number and figure.