Validity and Reliability
To determine if a test is valid, inter-tester, as well as intra-tester reliability, must be determined. Inter-tester reliability is being calculated by comparing test-values of the same subject by at least two different testers. Thus, intra-class correlation coefficients (ICCs) of how “equal” the test results are can be shown.
The strength of the correlation coefficients are commonly interpreted as [1, 5]:
- 0 = zero
- 1- 0.3 = weak
- 4- 0.6 = moderate
- 7-0.9 = strong
- 0 = perfect
Riemann et al.  examined inter-tester validity using repeated-measures analyses of variance (ANOVAs) with three testers who were each blinded against the results of the other testers and performed each test twice. Test repetitions were 48 hours apart .
They were able to show very good inter-tester reliability with ICCs ranging from 0.70-0.92. While the landing error scores showed no significant difference between the testers (ICC 0.92 and 0.92), the balance error scores differed significantly between two of the three testers resulting in slightly lower ICCs of 0.70 and 0.74. Still, even the lowest value (0.70) is still in the “strong” correlation category.
Until 2017, the intra-tester reliability of the MSLHST had not been investigated. Sawle et al.  conducted their intra-rater reliability study with one investigator in a single session. Their findings show an ICC-range between 0.72-0.88 that point towards good to excellent reliability of repeated tests. Other than for Riemann et al. , this study found better reliability scores for balance (ICC 0.88 and 0.87) instead of landing scores (ICC: 0.72 and 0.78) .
Both studies reflect differences in score reliability between balance and landing scores. As the MSLHST assesses the sum of the two scores, and both the inter-rater and intra-rater ICCs are in clinically acceptable standards, the test can be recommended for inclusion in future clinical trials of recreationally active participants and athletes [4, 9].
A test is only valid if it is reliable and can actually offer information that is relevant to what the test sets out to test. The MSLHST aims to assess an athlete’s balance. Balance and/or proprioceptive exercises are tools for injury prevention and rehabilitation . Knee instability is associated with one-legged jumping performance . Thus, the MSLHST consists of repeated forward and sideways one-legged jumps, and it is considered to challenge the athlete in a way which reflects common forces and manoeuvres that are not only performed in sports , but also help determine if a player obtains an injury or not . As a result, the MSLHST is therefore regarded a valid balance assessment tool.