The old surveys weren't any good, so they’ve created a new survey. Psychometric soundness refers to the instrument's reliability and validity. There are several ways to assess an instrument's characteristics, but, in general, reliability refers to the instrument's consistency (do people get consistent results if they take it more than once? do interpreters assess a subject's score in the same fashion?), while validity refers to the instrument's ability to measure the behavioral or mental construct it purports to measure. How do we know it’s valid (validity is the important part, because reliability is much easier to come by)? Simple:
“One problem (with previous research) is the lack of a psychometrically sound instrument for the measurement of bullying and victimization.”
What this means is this: They compared subjects' scores on the new instrument to scores on other instruments designed to measure the same construct (bullying). Subjects' scores on the instruments were similar. So, we know our new instrument overcomes the problem of a “lack of a psychometrically sound instrument” because our instrument relates well to all those other psychometrically unsound instruments. Go team.
“Significant Kruskal-Wallis tests of relationships between PIPS scales and items on the Olweus Bullying/Victimization Questionnaire and the Strengths and Difficulties Questionnaire supported concurrent validity.”