Students Struggled With…

• Using the correct t* critical value when calculating a t interval.

• Deciding between μ1- μ2 and μdiff.

Remedies…

• 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