The validity of this study could be improved by measuring the outcomes of both study groups concurrently. Validity, or the trustworthiness of a study's results, can be threatened by many factors, including errors in sampling, measurement, and data analysis. Systematic error results from bias that influences the study findings in a certain direction. Systematic error must be addressed by eliminating sources of bias, and doing so is a primary goal of study design. Seasonal variation in asthma symptoms is widely recognized, and in this study, the separation of study groups into summer and winter months is a systematic error that could account for the different peak-flow rates and quality-of-life scores between groups. This represents a potentially significant bias that could threaten the validity of the study outcomes. Therefore, this study could be improved by measuring outcomes for both study groups at the same time of year in order to eliminate this potential source of bias.

Including patients with COPD in the study would not improve the study's validity regarding the impact of meditation on the outcomes of patients with asthma.

Increasing the sample size and precision of measures would be effective in reducing the impact of random errors, but not systematic errors.