BACKGROUND In systematic reviews and meta-analysis, researchers often pool the results of the sample mean and standard deviation from a set of similar clinical trials. A number of the trials, however, reported the study using the median, the minimum and maximum values, and/or the first and third quartiles. Hence, in order to combine results, one may have to estimate the sample mean and standard...

BACKGROUND Cluster surveys provide rapid but representative estimates of key nutrition indicators in humanitarian crises. For these surveys, an accurate estimate of the design effect is critical to calculate a sample size that achieves adequate precision with the minimum number of sampling units. This paper describes the variability in design effect for three key nutrition indicators measured i...

increases. Taking this characteristic into consideration, we could confront the following circumstances: when the sample size is very small, we obtain a P-value of the normality test greater than 0.05 in most cases, so we conclude that the data are from a normally distributed population even though it apparently looks like a non-normal distribution. And when the sample size is very large, we fr...

‘How many participants do I need for my study?’ During many years of providing statistical support to clinical researchers, this has been one of the most frequently asked questions. It is posed by medical students preparing dissertation projects through to seasoned professors preparing major grant proposals. The repetition of this question can be frustrating, but does at least indicate that the...

Nutritional environments, particularly those experienced during early life, are hypothesized to affect longevity. A recent cross-taxa meta-analysis found that, depending upon circumstance, average longevity may be increased or decreased by early-life dietary restriction. Unstudied are the effects of diet during development on among-individual variance in longevity. Here, we address this issue u...