We got pretty good of always asking the students for each condition"what does it let us do?". We should really do the same thing every time we have them write down t - "why t* instead of z*?". This way, we have plenty of opportunities to discuss that we are estimating two values (mean and standard deviation) instead of just one. 

Make sure the homework includes a variety of additional displays. We want the students going back to Unit 1 when we shows dotplots, stemplots, boxplots, and histograms to think about how we could use all these displays to check conditions.