I'm a journalist researching a story for a mental health publication. A number of studies I'm looking at give their results in terms of "t tests." When I searched on the Web, I found a number of sites that could tell me how to calculate a t test ... but none that told me how to interpret the number once you got it. What does this value mean?

Here's an example.

In a study of psychiatric inpatients taking yoga classes, mean scores on a standard test for tension-anxiety went from 5.7 to 3.33. The researchers calculate this has a t-value of 6.67.

My question: how am I supposed to interpret that t-value? What does that number mean? Why is it more important/valuable than just a percent change? I'm tempted to just calculate the percent change and use that when I'm writing up my story since it's a figure a lot more people will be able to understand ... would that be correct to do?

Thanks for whatever help you can offer!