[gov2001-l] PS1 Briefing

Hi 2001, Solutions to problem set 1 are posted to the course website. We'll hand back your hardcopies in section on Thursday, and for this problem set I'll email a brief note and grade to those of you who submitted the entire problem set electronically. A couple of notes: Please use the solutions on the website as a guide for future problem sets. In particular, note how there are two files, one with R code (run-able; it's a file we can open and run as-is in R) and one with solutions and explanations. Submitting a separate R file is important so we can easily run your code and see where things went awry (or well, of course). If you use R to calculate something (such as a probability), include the actual value that R estimates in your write-up; don't just include the code without its output. Many of you had clever approaches to the birthday problem- good work. In the solutions we show two ways of estimating the room sizes in problem 2. Even if you generated all correct answers, take a look at the solution code. All of you can benefit from making your code more efficient. Common mistakes on this problem set include 1d, 2a, 2b and 3d. In 1d, a common error resulted from forgetting which gender corresponded to 1's and which to 0's. In both parts of problem 2, a common difficulty was figuring out how to find triplicate birthdays without counting two pairs of birthdays. (We discuss this problem in the R file to the solutions). Another mistake on 2 involved testing a few room sizes without resetting the counter for 'samedays' so the estimate for the number of required people was too low. In 3d, some struggled with drawing simulated datasets- you can review the solutions and also the R code from section 2 for a slick way to sample from a dataset. And finally, don't worry if your solutions were not exactly those posted on the solutions- these are all simulated estimates, so some variance is expected and perfectly fine. One problem set down... Jenn