Week 6 - Homework

For this homework, we will use the Palmer Penguins dataset. It contains information about three penguin species, living in the Palmer Archipelago. For each penguin, measurements include:

• Bill length and bill depth (in mm)
• Flipper length (in mm)
• Body mass (in grams)
• Sex and the island where it was observed
• Study year

The goal is to explore, manipulate and visualize these data in R while practicing the concepts learned in class.

0. Set up your workspace.

Create a new R Project called penguins_analysis and save the dataset file penguins.csv inside a folder named data in your project.

1. Import the penguins.csv dataset, name the imported data as penguins.

2. Insepct the imported data:

• How many rows and columns are there?
• Recode the species, island and sex as factors

3. Which species contains the most data?

4. Extract penguins of “Gentoo” species which live on the “Biscoe” island.

5. Create a new column bm_kg which stores the body mass in kilogram.

6. Which species shows the highest average body mass in kilogram?

7. Use scatter plot to visualise the body mass (in kg) and the bill length:

• Color the point by species.
• Increase the point size to 2.5.
• Replace the axis’ label by “Body Mass (kg)” and “Bill Length (mm)”.
• Remove the legend title.
• Use theme_minimal().
• Put the legend on the top of the figure.

What is your observation for Adelie and Chinstrap penguins?

8. Based on your observation from question 7, test if your hypothesis is statistically valid (using significance level at 5%).

Hints:

• Check the distribution of body mass or bill length, test the normality of data distribution of each species.
• If both group are normally distributed, use a t-test (?t.test); If one or both groups are not normally distributed, use a Wilcoxon rank-sum test.
• Report the p-value and state your conclusion in one sentence.

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The homework correction is available here: link