Require students write the specific formula for a t interval. This extra step may remind them that they need a t* instead of a z* which was the most common value they used instead.

To help decide between these procedures, students should ask themselves a

• How many samples do I have?

  • 0ne. μdiff

  • Two. μ1- μ2 (usually) Watch out for two samples that pair individuals.

• Can any piece of data in the first group be compared to any piece of data in the second?

  • Yes. μ1- μ2

  • No, they must stay in pairs. μdiff

• Do they reference pairing the data?

  • Yes. μdiff

  • No. μ1- μ2