Hello, my name is...

Prof. Dhrumil Mehta

dm3494@columbia.edu

@dmil

📍Numeracy

📍Statistics

📍Polling Data

Toaday

About Me:

Columbia University Graduate School of Journalism
Teach in Data MS & Advisor for CS + Journalism Dual MS
Assistant Director, Tow Center for Digital Journalism
Harvard Kennedy School
Visiting Associate Professor of Public Policy
Formerly:
- Database Journalist, Politics @ FiveThirtyEight
- Software Development Engineer @ Amazon
- Education
  - BA in Philosophy
  - MS in Computer Science

Every Wednesday in Brown Inst.

jschoolai.club

Not All Numbers Are Created Equal

http://numlock.news/

Let's take a look at this semantic map of Numlock News

https://data4news.com/numlock-nlp

Numlock News

https://www.numlock.com/about

Let's take a look at this semantic map of Numlock News

https://data4news.com/numlock-nlp

Numlock News

https://www.numlock.com/about

Pick a number you find interesting. Copy and paste the whole snippet (including the links) into this padlet.

https://padlet.com/data4news/numlock

We will come back to this later

Learning Objectives

There are different kinds of numbers that must be interpreted and presented differently

✔️ Identify what kind of number you're dealing with

✔️ Understand it's limitations

✔️ Know what kinds of questions to ask of it before reporting on it

Not All Numbers Are Created Equal

Counts and Measurements

Summary Statistics

Probabilities

Inferential Statistics

Indexes

Scaled Numbers

Election Forecast

a very complex kind of probabilistic number

https://www.natesilver.net/p/nate-silver-2024-president-election-polls-model#footnote-anchor-2-146002606

https://www.natesilver.net/p/nate-silver-2024-president-election-polls-model#footnote-anchor-2-146002606

https://fivethirtyeight.com/features/how-fivethirtyeights-2020-presidential-forecast-works-and-whats-different-because-of-covid-19/

Methodological Choices

I'm sure these aren't the only kinds of numbers...

...but they're all very different from one another

more methodological choices to vet

your income this year
(count)
the average graduating salary of everyone
in the last class
(summary statistic - descriptive)
the average income of all Americans
(summary statistic - inferential)
average income of a journalist anywhere in the world
(index)
forecasted journalist income in 10 years given assumptions about world economy
(probabilistic forecast)

Before you cite a number:

What is the original source of this number?
- Who first collected it and why?
What kind of number is it?
A count? a summary? a prediction? an estimate? an inferential statistic? an index?
How was it acquired or calculated?
What is the universe of data that it comes from?
What methodological choices were in inherent in
- creating the number
- selecting the number to be presented

What methodological choices are you making by finding/selecting/calculating/presenting this number?

Let's take come back to this padlet

Numlock News

https://www.numlock.com/about

https://padlet.com/data4news/numlock

In the comment for the number you picked, write :

1. what kind of number it is

2. what you'd want to know about this number before your cite it in your reporting

Learning Objectives

✔️ There are different kinds of numbers that must be interpreted and presented differently

Not All Numbers Are Created Equal

Intro to Stats for Journalists

Learning Objectives

✔️ Statistics summarize datasets just like a paragraph can summarize a story. Some things are lost in the process.

✔️ It's important to determine if the summary statistic does a good job of summarizing the underlying distribution before you cite it.

Statistics

source: http://www.differencebetween.net/language/words-language/difference-between-descriptive-and-inferential-statistics/

source: https://differencebetweenz.com/difference-between-descriptive-and-inferential-statistics/

source: https://www.geeksforgeeks.org/difference-between-descriptive-and-inferential-statistics/

Summary Stats

👻 Scary Math Symbol?

👍 Seems fine!

Mean

Ben Orlin — Math with bad drawings

Weighted Average

Text

https://www.cuemath.com/weighted-average-formula/

Example

https://projects.fivethirtyeight.com/biden-approval-rating/

Examples

Averages are weighted by the square root of the number of polls that a particular pollster conducted for that particular type of election in that particular cycle.

So, how did the polls do in 2024? It’s complicated | SilverBulletin