* Mendota Ice Exercises *---------------------- * Setup: read the data into Stata with these commands infile str7 winter str6 close str6 open days using "http://www.ssc.wisc.edu/~hemken/Stataworkshops/Mendota2011.raw" generate year=real(substr(winter, 1, 4)) * Problem 1 *---------- * What what was the longest ice fishing season on record? * How many days long was it, and what was the year? * What was the shortest season? * Problem 2 *---------- * How common has it been to have 120 or more days of ice cover? * * (Hint: create an indicator.) * Problem 3 *---------- * Would a person who grew up in the period 1900-1920 (like my * grandparents) be justified in thinking that "today's kids * have it easy"? Compare the mean duration of ice cover for * 1900-1920 versus 1990-2010. * * (Hint: You could drop unneeded observations with a "drop if" * command, or filter them with an indicator variable and * an "if" clause.) * Problem 4 *---------- * When should we expect the Lake to open this spring? * * (Hint: convert the variable "open" to a day-of-the-year * by using the mdy() function or the date() function * and the %td format. Just getting the components for * mdy() or date() will be the hardest part of this * exercise. Use a constant year. Take the mean for a * simple prediction, and construct an optional confidence * interval. * If you know regression, predict a result for "2010".