The phrase "lack validity" is correct and usable in written English.
You can use this phrase when you want to state that something does not have sufficient evidence or proof to be accepted as true or accurate. For example: "The witness's testimony lacked validity, and the court ultimately found the defendant not guilty."
However, many of the image studies lack validity or generalization.
Sourcing: The sources of your data should always be cited, otherwise the end product will lack validity.
Current time prediction models lack validity when the handled object's mass exceeds 2 kg.
Critics complain that it often characterizes everyday behaviors as abnormal, and that it continues to lack validity, whether or not the issue of reliability has been definitely resolved.
Several studies highlight dissatisfaction with WBAs, and some feel they lack validity and reliability and exist as a "tick-box exercise".
Dysfunctional turning is common in Parkinson's Disease but most existing measurement tools are inadequate for this group, lack validity and are laboratory-based.
These and similar research findings suggest the Global Slavery Index lacks validity.
And just because there is no detailed blueprint for how to achieve the full vision, does mean it lacks validity.
Currently used classification systems are largely descriptive, lacking validity, reproducibility, treatment considerations, and prognostic information.
There is a real risk that the Department for Education's statistically inadequate approach will lead to distorted results, misleading rankings and a system which lacks validity and is unnecessarily vulnerable to being gamed.
Patient-reported seizure frequency is essential for therapy management and clinical research but lacks validity mainly due to seizure-induced seizure unawareness.
