Data

What is Data?

Data is a collection of facts, such as numbers, words, measurements, observations or even just descriptions of things.

Qualitative vs Quantitative

Data can be qualitative or quantitative.

• Qualitative data is descriptive information (it describes something)
• Quantitative data is numerical information (numbers)

Quantitative data can be :

• Discrete data can only take certain values (like whole numbers)
• Continuous data can take any value (within a range)

Put simply: Discrete data is counted, Continuous data is measured

Example: What do we know about Arrow the Dog?

Qualitative:

• He is brown and black
• He has long hair
• He has lots of energy

Quantitative:

• Discrete:
  • He has 4 legs
  • He has 2 brothers
• Continuous:
  • He weighs 25.5 kg
  • He is 565 mm tall

To help you remember think "Quantitative is Quantity"

More Examples

Qualitative:

• Your friends' favorite holiday destination
• The most common given names in your town
• How people describe the smell of a new perfume

Quantitative:

• Height (Continuous)
• Weight (Continuous)
• Petals on a flower (Discrete)
• Customers in a shop (Discrete)

Collecting

Data can be collected in many ways. The simplest way is direct observation.

Example: Counting Cars

You want to find how many cars pass by a certain point on a road in a 10-minute interval.

So: stand near that road, and count the cars that pass by in 10 minutes.

You might want to count many 10-minute intervals at different times during the day, and on different days too!

We collect data by doing a survey.

Census or Sample

A Census is when we collect data for every member of the group (the whole "population").

A Sample is when we collect data just for selected members of the group.

Example: 120 people in your local football club

You can ask everyone (all 120) what their age is. That is a census.

Or you could just choose the people that are there this afternoon. That is a sample.

A census is accurate, but hard to do. A sample is not as accurate, but may be good enough, and is a lot easier.

Language

Data or Datum?

The singular form is "datum", so we say "that datum is very high".

"Data" is the plural so we say "the data are available", but data is also a collection of facts, so "the data is available" is fine too.