Compare Means

Because lifespan is a continuous variable, it is straightforward to apply a t-test to compare the maximum lifespan between two groups, or to apply ANOVA to compare maximum lifespan among multiple groups. We call this the conditional t-test (CTT) approach. It can be easily generalized to compare means across multiple groups by conditional ANOVA (Goodrick et al., 1990). If the lifespan of the sample is normally distributed, it is apparent that the distribution of the lifespan in the upper percentile has a truncated normal distribution, not a symmetric distribution. We already know that the t-test is a parametric method and that one of its assumptions is that the data are derived randomly from a normally distributed population. Therefore, in this instance, the application of the CTT is questionable. In fact, in a simulation study, Wang et al. (2004) showed that the CTT

does have an inflated type I error rate and is invalid for comparing maximum lifespan.

Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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