The field trial was arranged in a randomized factor design with three replicate treatments for each factor.
Comparison across groups was carried out by analysis of covariance (ANCOVA) with the follow-up measurement as dependent variable, the randomized agent as factor, and the baseline measurement as covariate (or as categorical co-factor in case of NYHA class).
Twenty-nine headultsadults participated in a randomized, two-factor cross-over study with or without biking exercise for 180 min and with exposure to particles (NC 6169-15362/cm) or filtered air (NC 91-542/cm) for 24 hr.
It is a randomized, two-factor, single-blind, longitudinal effectiveness trial where low-income families (1168) were randomly assigned to receive either (1) Family Healthy Lifestyle plus Family Recreation service integration (Comprehensive), (2) Family Healthy Lifestyle service integration, (3) Family Recreation service integration, or (4) existing services.
Randomization avoids bias (whether conscious or unconscious); with randomized allocation, predictive factors (known and unknown) tend on average to be balanced between treatment groups.3,8,11 Also, randomization provides a valid basis for statistical tests of significance.3 These concepts are discussed further later.
In randomized trials these factors are more standardized.[70] Third, respondents in observational studies may be misclassified according to their self-reported protein intake, which may dilute the protein-BP association.[71] Fourth, for investigation of long-term effects of protein on BP, an observational study is the most suitable type of study, because of the costs of a trial.
Also our patients were randomized, hence many factors that could have affected our findings were randomly distributed between the intervention and control groups.
To optimize N utilization and increase grain yield, we conducted a two-year field experiment with single-factor randomized block designs of a maize-soybean intercropping system (IMS).
Methods that adjust the intention-to-treat analyses according to rates of noncompliance and other factors — randomized-based efficacy estimation methods — avoid selection bias by basing the analyses on the original groups [1], [3], [8] [11], [28] [32].
In order to clarify the significance of each etiologic factor, randomized controlled trials are necessary.
