Re-do Episode 4 exercises

[kaijagahm]

Relevant learner feedback:

• "I think you all could cut down on the questions that require you to build multiple new datasets and instead it could be more helpful to build one data set and add new variables to address more than one question."
• "The exercises we did in R took a while, so those could be shorter, simpler, or build on prior exercises."
• "Building off of the above comment, having the same or similar example dataset that we build off of throughout may be useful for the flow of ideas and making it feel a bit less choppy"

This is going to relate a lot to #15 and #10 and will be part of a broader discussion about structure/flow for sure.

[kaijagahm]

From feedback: Lesson is very long, decide what can be cut vs. whether this needs to be a long lesson.

[xortizross]

• Needs fewer exercise sections, make it clear which ones are extra for faster learners and do not go into these during the lesson
• Clarify the purpose of each exercise, what is the LO they are addressing?
• Maybe move exercise 1 and 4 to examples. Discuss in light of comment to do exercises together.
• Make sure examples are building from each other as you go through the lesson. Start with simpler.
• Clearly indicate time allocated for the exercises