Determine whether the following statement is true or false: We use a $t$ distribution when we don't know $\sigma$ and a $z$ distribution when we do. True False Submit Question

Step 1 ：The question is asking about the conditions under which we use a t-distribution and a z-distribution in statistics.

Step 2 ：The t-distribution is typically used when the population standard deviation (σ) is unknown and the sample size is small.

Step 3 ：The z-distribution, on the other hand, is used when the population standard deviation is known or the sample size is large.

Step 4 ：Therefore, the statement is true.

Step 5 ：Final Answer: \(\boxed{True}\)