Number of observations. The smaller the number of observations, the more difficult it is to detect the effect of an intervention. Example: Terri was able to collect only two baseline observations and...

Number of observations. The smaller the number of observations, the more difficult it is to detect the effect of an intervention. Example: Terri was able to collect only two baseline observations and three intervention observations for her client. The small number of observations made it unclear as to whether substantial changes actually had occurred so that it was difficult to determine whether the intervention was effective.