Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE chip_model (RAM_MiB INTEGER, model_name VARCHAR, chip_model VARCHAR); CREATE TABLE phone (RAM_MiB INTEGER, model_name VARCHAR, chip_model VARCHAR)
### Question:
Find the average ram mib size of the chip models that are never used by any phone.
### Answer:
SELECT AVG(RAM_MiB) FROM chip_model WHERE NOT model_name IN (SELECT chip_model FROM phone)