The phrase "earlier than average" is correct and can be used in written English.
It is commonly used to describe something that occurs or happens before the usual or expected time, date, or amount. Example: The sales for the new product were earlier than average, surpassing our expectations and breaking previous records.
It matures in 105 days, four weeks earlier than average.
This corresponds to the abrupt increase in rainfall amounts around early May when the rainy season begins earlier than average (Fig. 4b).
That's a bit earlier than average, but not the earliest reported in recent years.
According to the data, the Arctic sea ice melt season is running as much as one month earlier than average.
But Monday's snow and a dusting that followed Tuesday were heavier and earlier than average years and fell in important watersheds, forecasters said.
(Interestingly, the same study found that girls growing up in homes with males unrelated to them got their periods earlier than average, suggesting that a non-related male may speed up sexual maturity).
The American Cancer Society recommends women with a relative affected by breast cancer before 50 years, with two or more relatives affected by breast cancer and with a relative affected by two independent breast cancers to start 10 years earlier than average-risk women, or 5 10 years earlier than the youngest patient in the family (Smith et al, 2003).
Individuals who have a genetic disposition to alcoholism are also more likely to begin drinking at an earlier age than average.
Interestingly, the mean peak phase for RVE8-regulated EE-containing CCGs is significantly earlier than that of all EE-containing CCGs, indicating that RVE8 regulates a subset of evening genes that have slightly earlier phase than average EE-containing evening genes.
Hence, after several generations in hypergravity, the average cell begins to express the rpoS gene earlier than the average cell at normal gravity conditions (Figure 3).
Certain professions such as railway workers or staff at the national opera have privileged deals allowing them to leave their jobs earlier than the average citizen.
