The phrase "are less rigorous than" is correct and usable in written English.
It can be used to compare the level of strictness or thoroughness between two subjects or concepts.
Example: "The new guidelines are less rigorous than the previous ones, allowing for more flexibility in implementation."
Alternatives: "are not as strict as" or "are more lenient than".
In some areas, like the length of student-teaching placement, Dr. Robinson said, the council's standards are less rigorous than what many education schools require.
The procedures for screening contractors on projects financed by the city's Economic Development Corporation, as the stadium was, are less rigorous than for projects built and paid for by the city.
The funniest scenes have some of the improvised, pseudo-vérité flavor of Christopher Guest's "Best in Show," but Mr. Ferrell and Mr. McKay are less rigorous than Mr. Guest and his collaborators, preferring easy laughs to carefully turned comic insights.
The Food and Drug Administration cannot guarantee the safety of the nation's drug supply because it inspects few foreign drug manufacturers and the inspections it does carry out abroad are less rigorous than those performed in this country, witnesses told a Congressional subcommittee yesterday.
Up to 200 tests are carried out each year as part of the ECB's programme but county cricket's current procedures are less rigorous than both professional football and rugby in England.
The general consensus in the education community seems to be that even though online courses have merit, they are less rigorous than classroom settings.
Some analysts also said the measure was less rigorous than many had feared.
But dealers sometimes fit the cars with dealer plates, often obtained from states like Pennsylvania, where applying is less rigorous than in New York.
It was less rigorous than the butterfly but not as geriatric as the breaststroke, and after long enough you still got tired – marvellously so.
European and American officials have said the control process was less rigorous than they had hoped for, a complaint echoed repeatedly by Abdullah's team.
Responding to the F.D.A. decision, Mr. DiPiazza noted that the recent F.D.A. review was less rigorous than the agency's 1997 review.
