LECTURE 1 · INTRODUCTION TO DATA SCIENCE

Turning data into decisions

Welcome! No coding or statistics background needed, just curiosity.

What is data science?

Using data to answer questions and make better decisions.

  • Math & statistics: tell a real pattern from luck
  • Coding: handle data too big for a spreadsheet
  • Domain knowledge: ask questions that matter

Data science lives where all three overlap.

Math &Statistics CodingDomain knowledge Machinelearning Traditionalresearch Danger zone! Data Science Adapted from Drew Conway's data science Venn diagram (2010)
Md Mahbub E NoorLecture 1: Turning data into decisionsUniversity of Barishal2 / 13

What is data?

Most data science starts with a table. Here are four text messages, described as data.

messagelengthcontains "free"has a numberlabel
Claim your FREE gift now24yesnospam
Class moved to room 30523noyesham
Free entry: text WIN to 8008629yesyesspam
Ok, see you at the library26nonoham
One row = one example

a single message, patient or sale

One column = one feature

a measured property, used as input (X)

Label column = the answer

what we want to predict (y)

A model learns how the feature columns relate to the label, then predicts the label for new rows. In Lecture 5 this table has 5,572 rows; in Lecture 6 we call the features X and the label y.

Md Mahbub E NoorLecture 1: Turning data into decisionsUniversity of Barishal3 / 13

Why learn data science?

1

Data is everywhere

Every tap, purchase and scan leaves a data trail.

2

Better decisions

Swap guesses for evidence: what to stock, whom to treat first.

3

Skills that travel

Health, finance, farming, research: all need people who read data.

Md Mahbub E NoorLecture 1: Turning data into decisionsUniversity of Barishal4 / 13

Traditional software vs. data science

TRADITIONAL SOFTWAREA person writes the rules
RulesData
➜
Program
➜Answers
DATA SCIENCEThe computer learns the rules
DataAnswers (examples)
➜
Learning
➜Rules (a model)
Traditional softwareData science
ExampleCalculator, payroll systemSpam filter, face unlock
OutputExact, the same every timeA prediction, with some uncertainty
Best whenThe rules are known exactlyThe rules are too complex to write by hand
Md Mahbub E NoorLecture 1: Turning data into decisionsUniversity of Barishal5 / 13

Live demo: can you write rules that catch spam?

1

Write rules

Keywords like "free" catch 4 of 8 messages. Every fix opens a new hole.

2

Let it learn

A model trained on 30 labeled messages learns its own clues.

3

Try your own

Type any message and see which words look spammy to the model.

Md Mahbub E NoorLecture 1: Turning data into decisionsUniversity of Barishal6 / 13

The data science lifecycle

1Ask
Will the river flood this week?
➜
2Collect
River levels and rainfall
➜
3Clean
Fill missing sensor readings
➜
4Explore
Plot rain vs. river level
➜
5Model
Forecast tomorrow's level
➜
6Share
Early alerts to farmers

A loop, not a line: exploring often sends you back to ask a better question. Modeling is one step of six.

Md Mahbub E NoorLecture 1: Turning data into decisionsUniversity of Barishal7 / 13

You already use data science every day

1

Recommendations

What will you watch next? Learns from your history and what similar people enjoyed.

2

Healthcare

Does this X-ray look healthy? Learns from past scans labeled by doctors.

3

Finance

Is this payment fraud? Learns from normal spending and past fraud cases.

4

Maps and travel

How long will this trip take? Learns from live speeds of phones on the road.

Md Mahbub E NoorLecture 1: Turning data into decisionsUniversity of Barishal8 / 13

The road ahead: from zero to a spam detector

LectureTopicYou will be able to
1What is data science?Explain what data science is and how models learn
2.1 to 2.3Getting started, Python basics, debuggingRun code offline and online; read and fix errors
3.1 to 3.3Decisions, lists and tuples, loopsBuild a rule-based spam filter, and see it fail
4.1 to 4.2Functions, dictionariesCount words and score messages from examples
5Real data with pandasLoad, clean and explore 5,572 real messages
6Build a spam detectorTrain, test and honestly evaluate a real model
[7 onwards][Remaining course topics][To be added]
Md Mahbub E NoorLecture 1: Turning data into decisionsUniversity of Barishal9 / 13

How this course works

ItemDetails
Classes and labs[Days, times, rooms]. Labs use Jupyter Notebook on the lab PCs (offline)
At homeGoogle Colab (online), or Jupyter if you install Anaconda on a laptop
Assessment[Homework __%] · [Quizzes __%] · [Midterm __%] · [Project __%] · [Final __%]
HomeworkAfter every lecture from Lecture 2. Submit your .ipynb file on [LMS / Google Classroom]
Late work[Late policy]
HelpOffice hours: [day, time, room] · Contact: [email]
Md Mahbub E NoorLecture 1: Turning data into decisionsUniversity of Barishal10 / 13

Using AI tools in this course

1

Allowed

[For example: asking an AI to explain an error message or a concept, like a tutor.]

2

Not allowed

[For example: submitting code or answers generated by an AI as your own work.]

3

Always

You must be able to explain every line you submit. [Say whether and how AI use must be disclosed.]

Md Mahbub E NoorLecture 1: Turning data into decisionsUniversity of Barishal11 / 13