What is a t-score?
A t-score is closely related to its cousin the z-score
A z-score is based upon a Standard Normal distribution with a mean of 0 and standard deviation of 1.
The t-distribution was created by William Gossett to take into account small sample sizes. Like the Standard Normal, the t-distribution is perfectly symmetric about a mean of 0.
As the sample size (n) increases toward infinity, the t-distribution approaches the standard normal distribution.
The chart below compares the two:
As you can see, the t-distribution (n=12) is flatter and more spread out.
When calculating a confidence interval , the t-distribution will result in a wider interval compared to the z-distribution. This is more conservative given the smaller sample size and increases the interval to better capture the true population parameter.
Hope that helps