"a previous one" is correct and usable in written English.
You can use it to refer to something earlier in a sequence such as a prior event or comment. For example: "I had a disagreement with my neighbor about parking in our shared driveway, but a previous one was about the noise from her dog."
The new target was set after a previous one on closing the gap in preschool levels failed in 2013.
The earthquake was the second in a week to hit Lombok following a previous one on 29 July, which killed 16 people and damaged numerous houses.
The authors developed a formula based on a previous one derived by Sir Ronald A. Fisher (1890 1962).
But most of the bail hearing today, and a previous one in December, focused on the question of espionage, of which he is not accused.
He collected his second booking of the game for a foul on Henri Lansbury following a previous one for dissent.
This paper complements a previous one [1] about toluene adsorption on a commercial spherical activated carbon and on samples obtained from it by CO2 or steam activation.
A previous one-dimensional model of the SCR monolith reactor has been extended to include the treatment of the undesired SO2 oxidation reaction.
The donations eclipsed a previous one-day fund-raising record of $5.7 million, set by Senator John Kerry in 2004 after he accepted the Democratic nomination for president.
A previous "one-off" sale in 2008 was criticised by some as driving up demand, but defended by others as providing funds for elephant protection.
The 1 million new customers who picked health plans last week compares with a previous one-week record of just under 900,000 two years ago.
Panetta served a previous one-year stint as a Corinthian director, resigning in 2009 when he was named CIA director.
