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Understanding Lego sets popularity

📖 Background

You recently applied to work as a data analyst intern at the famous Lego Group in Denmark. As part of the job interview process, you received the following take-home assignment:

You are asked to use the provided dataset to understand the popularity of different Lego sets and themes. The idea is to become familiarized with the data to be ready for an interview with a business stakeholder.

💾 The data

You received access to a database with the following tables. You can also see above a visualization of how the tables are related to each other. (source):
inventory_parts
  • "inventory_id" - id of the inventory the part is in (as in the inventories table)
  • "part_num" - unique id for the part (as in the parts table)
  • "color_id" - id of the color
  • "quantity" - the number of copies of the part included in the set
  • "is_spare" - whether or not it is a spare part
parts
  • "part_num" - unique id for the part (as in the inventory_parts table)
  • "name" - name of the part
  • "part_cat_id" - part category id (as in part_catagories table)
part_categories
  • "id" - part category id (as in parts table)
  • "name" - name of the category the part belongs to
colors
  • "id" - id of the color (as in inventory_parts table)
  • "name" - color name
  • "rgb" - rgb code of the color
  • "is_trans" - whether or not the part is transparent/translucent
inventories
  • "id" - id of the inventory the part is in (as in the inventory_sets and inventory_parts tables)
  • "version" - version number
  • "set_num" - set number (as in sets table)
inventory_sets
  • "inventory_id" - id of the inventory the part is in (as in the inventories table)
  • "set_num" - set number (as in sets table)
  • "quantity" - the quantity of sets included
sets
  • "set_num" - unique set id (as in inventory_sets and inventories tables)
  • "name" - the name of the set
  • "year" - the year the set was published
  • "theme_id" - the id of the theme the set belongs to (as in themes table)
  • num-parts - the number of parts in the set
themes
  • "id" - the id of the theme (as in the sets table)
  • "name" - the name of the theme
  • "parent_id" - the id of the larger theme, if there is one

Acknowledgments: Rebrickable.com

💪 Challenge

Create a report to summarize your findings. Include:

  1. What is the average number of Lego sets released per year?
  2. What is the average number of Lego parts per year?
  3. Create a visualization for item 2.
  4. What are the 5 most popular colors used in Lego parts?
  5. [Optional] What proportion of Lego parts are transparent?
  6. [Optional] What are the 5 rarest lego bricks?
  7. Summarize your findings.
1 hidden cell

1. What is the average number of Lego sets released per year?

First, we observe the columns contained in the sets table.

Spinner
DataFrameas
sets
variable
SELECT *
FROM sets;

Then, we wonder. How many unique sets and/or releases does this dataset have? What is the temporal range analyzed?

Spinner
DataFrameas
df
variable
SELECT COUNT(set_num) AS total_released
FROM sets;
Spinner
DataFrameas
df
variable
SELECT MIN(year) AS first_year, MAX(year) AS last_year
FROM sets;

The dataset has 11,673 total set releases, with data from the year 1950 to the year 2017 inclusive.

Now, we can display the above by showing the total number of set releases per year.

Spinner
DataFrameas
sets_released
variable
SELECT year, COUNT(set_num) AS sets_released_per_year
FROM sets
GROUP BY year
ORDER BY year ASC;

To answer the question of average set releases per year, we must specify a temporal range.

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