From the course: Complete Guide to Excel Statistics with Copilot
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t-statistic vs. z-statistic
From the course: Complete Guide to Excel Statistics with Copilot
t-statistic vs. z-statistic
- [Instructor] By now we're pretty well acquainted with the normal distribution. We know that many populations are normally distributed. So if we have a sample with a large sample size, and if we know the population standard deviation, we can feel comfortable using the normal distribution and finding z-scores. But most of the time, we don't have the resources to gather a sufficiently large sample and rarely do we know the population standard deviation. Small sample sizes and no access to the population standard deviation, those are two forms of uncertainty. If we gather 100 samples, and each sample has a sample size of only five data points, we start to run into a problem. The distribution of the sample means won't exactly look like the normal distribution. The distribution curve would be a bit more flat and the tails would be a bit more fat. This is not the normal distribution. In other words, the z-distribution won't work, which is why we need something called the t-distribution…
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