4  Types of Variables

4.1 Components of a datset

  1. Each variable must have its own column.

  2. Each observation must have its own row.

  3. Each value must have its own cell.

4.2 penguins dataset

  1. How many variables and observations are there in the data set?

  2. What are the variable names?

Variable description

Variable name Variable description
species penguin species (Adélie, Chinstrap and Gentoo)
island island in Palmer Archipelago, Antarctica (Biscoe, Dream or Torgersen)
bill_len bill length (millimeters)
bill_dep bill depth (millimeters)
flipper_len flipper length (millimeters)
body_mass body mass (grams)
sex penguin gender (female, male)
year the study year (2007, 2008, or 2009)

Preview of the dataset

# A tibble: 344 × 8
   species island    bill_length_mm bill_depth_mm flipper_length_mm body_mass_g
   <fct>   <fct>              <dbl>         <dbl>             <int>       <int>
 1 Adelie  Torgersen           39.1          18.7               181        3750
 2 Adelie  Torgersen           39.5          17.4               186        3800
 3 Adelie  Torgersen           40.3          18                 195        3250
 4 Adelie  Torgersen           NA            NA                  NA          NA
 5 Adelie  Torgersen           36.7          19.3               193        3450
 6 Adelie  Torgersen           39.3          20.6               190        3650
 7 Adelie  Torgersen           38.9          17.8               181        3625
 8 Adelie  Torgersen           39.2          19.6               195        4675
 9 Adelie  Torgersen           34.1          18.1               193        3475
10 Adelie  Torgersen           42            20.2               190        4250
# ℹ 334 more rows
# ℹ 2 more variables: sex <fct>, year <int>

4.3 Types of Variables

4.4 Qualitative/ Categorical Variables

  • Describes categories or groups

  • Non-numeric (no numerical meaning)

  • Examples:

    • colors: red, blue, green
    • gender: male, female
    • types of animals: non-mammal mammal

Your turn: Identify qualitative variables in the penguins dataset.

4.5 Quantitative Variables/ Numerical Variables

  • Represents measurable quantities

  • Numeric

  • Examples:

    • Height in cm
    • Weight in kg

Your turn: Identify quantitative variables in the penguins dataset.

4.6 Discrete vs Continuous

Discrete

  • Represent countable quantities

  • Can take on only specific, distinct values (whole numbers)

  • No intermediate values between consecutive values

  • Examples:

  • Number of students in a classroom

  • Number of cars in a parking lot

  • Number of books on a shelf

Continuous

  • Represent measurable quantities

  • Can take on any value within a given range, including fractions and decimals.

  • Infinite number of possible values within a range.

  • Examples:

  • Height of individuals

  • Temperature

  • Time taken to complete a task

Your turn: Identify discrete and continuous variables

Variable name Variable description
species penguin species (Adélie, Chinstrap and Gentoo)
island island in Palmer Archipelago, Antarctica (Biscoe, Dream or Torgersen)
bill_len bill length (millimeters)
bill_dep bill depth (millimeters)
flipper_len flipper length (millimeters)
body_mass body mass (grams)
sex penguin gender (female, male)
year the study year (2007, 2008, or 2009)

4.7 Scales of measurement

4.8 Nominal Scale

  • The simplest measurement scale

  • Named variable levels

  • No numerical meaning

  • They have no natural order.

  • Categories are mutually exclusive.

  • The difference between values can’t be evaluated.

Examples

  • Blood type: O-, O+, A-, A+, B-, B+, AB-, AB+

  • Hair color: Blonde, black, brown, grey

  • District you live

4.9 Ordinal Scale

  • The simplest measurement scale

  • Named variable levels

  • No numerical meaning

  • They have a natural order.

  • Categories are mutually exclusive.

  • The difference between values can’t be evaluated.

Examples

Income: Low income, medium income, high income

Customer Satisfaction: Very Dissatisfied, Dissatisfied, Neutral, Satisfied, Very Satisfied

Grade: A+, A, A-, B+, B, B-

4.10 Interval Scale

These variables have

  • a natural order

  • a numerical meaning

  • a quantifiable difference between values

  • no true zero value

Examples

  • Temperature: Measured in Fahrenheit or Celsius

  • Marks: Measured from 0 to 100

4.11 Ratio Scale

These variables have

  • a natural order

  • a numerical meaning

  • a quantifiable difference between values

  • a true zero value

Examples

  • Height: measured in centimeters.

  • Weight: measured in kilograms.

4.12 Summary: scales of measurements

4.13 Exercise

Identify scales of measurement for each variable.

Variable name Variable description
species penguin species (Adélie, Chinstrap and Gentoo)
island island in Palmer Archipelago, Antarctica (Biscoe, Dream or Torgersen)
bill_len bill length (millimeters)
bill_dep bill depth (millimeters)
flipper_len flipper length (millimeters)
body_mass body mass (grams)
sex penguin gender (female, male)
year the study year (2007, 2008, or 2009)