This paper introduces the dhurdle command for Stata, a maximum-likelihood routine ( d2) to estimate the Cragg double hurdle model with either independent or dependent errors. We give a brief description of the procedure and its application to durable goods consumption and market participation...

A diagnostic test is used typically because it is cheaper, quicker or less invasive than the reference standard, but may not be as reliable. Diagnostic tests are evaluated against a reference standard (sometimes called "Gold Standard"), regarded as completely accurate. Commands diagt and diagti...

Biplots display correlations and differences in means and standard deviations of many variables on one graph, together with the values of the plotted variables and approximations of the Euclidean distance between the observations. Biplots are useful for identifying clusters of observations,...

The recent addition of support for the CMYK colour model to Stata 8 allows graphs from Stata to be used where colour separation is required for printing. This paper outlines work being done at the Office for National Statistics to use Stata for graphics in our flagship "Economic Trends"...

Systematic reviews of randomised trials are now widely recognised to be the best way to summarise the evidence on the effects of medical interventions. A systematic review may (though it need not) contain a meta-analysis, `a statistical analysis which combines the results of several independent...

Searches for genes using linkage analyses with genetic markers placed across the entire human genome are hypothesis-free experiments, which represent an extreme form of multiple testing. As such, the low p-values required to obtain nominal significance make accurate diagnostics essential to...

The Stata command xtreg estimates the random-effects linear regression model, for which the random effects are assumed to be normally distributed with zero mean and non-negative variance, s^2_{i,t}. Testing homogeneity across units is equivalent to testing the null hypothesis H_0: s^2_{i,t} = 0,...

Time-to-event endpoints are a common outcome of interest in randomised clinical trials. The primary analysis should usually be by intention-to-treat, giving an indication of the effectiveness of the intervention in a population as a whole. However, the benefit specifically for an individual...

Circular data are a large class of directional data, which are of interest to scientists in many fields, including biologists (movements of migrating animals), meteorologists (winds), geologists (directions of joints and faults), and geomorphologists (landforms, oriented stones). These examples...

A resultsset is a Stata dataset created as output by a Stata program. It can be used as input to other Stata programs, which may in turn output the results as publication-ready plots or tables. Programs that create resultssets include xcontract, xcollapse, parmest, parmby and descsave. Stata...