"results improved" is correct and usable in written English.
For example, "With the new training program in place, we saw immediate improvements in results."
Their liver function test results improved.
Throughout the period, school results improved.
"Our key stage 1 results improved dramatically this year.
They just went ahead and tried it, then looked to see if results improved.
Intriguingly, the pupils whose results improved most markedly were the poorest.
But as the results improved, the waiting list for organs grew.
Underwriting results improved at each of Berkshire's significant insurance businesses in both the first and second quarters of 2002.
Wells Fargo joins U.S. banks including Bank of America, Citigroup and JPMorgan Chase in saying results improved early this year.
Maths results improved not just for those getting a grade C or higher, but also for high achievers.
Results improved in year 3 and 5 reading, year 3 spelling, grammar and punctuation, and year 5 numeracy since 2008.
And Ford's results improved in Latin America and East Asia, although profit eroded at the company's European operations.
