What can a few measurements tell us?
This page helps a reader compare the sizes of three kinds of penguins. The question is whether a heavier penguin also has a longer bill. Body mass and bill length describe different parts of the animal, so one measurement may not tell the whole story.
Selection: the first six records with all four body measurements present for each species, in the source file's order. Record numbers count data rows, excluding the CSV header. All 18 selected records are from 2007.
The data
| Record | Species | Island | Bill length (mm) | Bill depth (mm) | Flipper (mm) | Mass (g) | Year |
|---|---|---|---|---|---|---|---|
| Row 154 | Gentoo | Biscoe | 50 | 16.3 | 230 | 5700 | 2007 |
| Row 156 | Gentoo | Biscoe | 50 | 15.2 | 218 | 5700 | 2007 |
| Row 157 | Gentoo | Biscoe | 47.6 | 14.5 | 215 | 5400 | 2007 |
| Row 158 | Gentoo | Biscoe | 46.5 | 13.5 | 210 | 4550 | 2007 |
| Row 153 | Gentoo | Biscoe | 46.1 | 13.2 | 211 | 4500 | 2007 |
| Row 155 | Gentoo | Biscoe | 48.7 | 14.1 | 210 | 4450 | 2007 |
| Row 282 | Chinstrap | Dream | 45.2 | 17.8 | 198 | 3950 | 2007 |
| Row 278 | Chinstrap | Dream | 50 | 19.5 | 196 | 3900 | 2007 |
| Row 2 | Adelie | Torgersen | 39.5 | 17.4 | 186 | 3800 | 2007 |
| Row 1 | Adelie | Torgersen | 39.1 | 18.7 | 181 | 3750 | 2007 |
| Row 281 | Chinstrap | Dream | 52.7 | 19.8 | 197 | 3725 | 2007 |
| Row 6 | Adelie | Torgersen | 39.3 | 20.6 | 190 | 3650 | 2007 |
| Row 279 | Chinstrap | Dream | 51.3 | 19.2 | 193 | 3650 | 2007 |
| Row 7 | Adelie | Torgersen | 38.9 | 17.8 | 181 | 3625 | 2007 |
| Row 280 | Chinstrap | Dream | 45.4 | 18.7 | 188 | 3525 | 2007 |
| Row 277 | Chinstrap | Dream | 46.5 | 17.9 | 192 | 3500 | 2007 |
| Row 5 | Adelie | Torgersen | 36.7 | 19.3 | 193 | 3450 | 2007 |
| Row 3 | Adelie | Torgersen | 40.3 | 18 | 195 | 3250 | 2007 |
A closer look at two records
| Measurement | Chinstrap, row 281 | Gentoo, row 154 |
|---|---|---|
| Mass (g) | 3725 | 5700 |
| Bill length (mm) | 52.7 | 50.0 |
| Flipper length (mm) | 197 | 230 |
The Gentoo in row 154 is 1975 g heavier and has a flipper that is 33 mm longer. But its bill is 2.7 mm shorter. Looking only at mass would miss this difference.
This comparison shows why it helps to use several columns together. It does not prove that every Gentoo has a shorter bill than every Chinstrap.
What the small sample suggests
The six Gentoo records have an average mass of 5050.0 g. The averages are 3587.5 g for the six Adelie records and 3708.3 g for the six Chinstrap records. In this selection, the Gentoo records are heavier.
The average bill lengths for Gentoo and Chinstrap are close: 48.15 mm and 48.52 mm. More body mass does not automatically mean more bill length. To make a broader claim, use the full dataset and check differences by sex, year, and island.
Glossary
- Species
- The kind of penguin recorded: Adelie, Chinstrap, or Gentoo.
- Bill length
- The measured length of the penguin's bill, in millimeters.
- Bill depth
- The measured depth of the bill, in millimeters.
- Flipper length
- The measured length of a flipper, in millimeters.
- Body mass
- The measured mass of the penguin, in grams. One thousand grams is one kilogram.
- Sample
- A selected part of a larger dataset. These 18 rows are not a random sample.