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  3. HarvardX Data Science Module 4 - Inference and Modeling

Exercise

Exercise 2. Pollster results for p

Create a new object called pollster_results that contains the pollster's name, the end date of the poll, the proportion of voters who declared a vote for Clinton, the standard error of this estimate, and the lower and upper bounds of the confidence interval for the estimate.

Instructions

100 XP
  • Use the mutate function to define four new columns: X_hat, se_hat, lower, and upper. Temporarily add these columns to the polls object that has already been loaded for you.
  • In the X_hat column, convert the raw poll results for Clinton to a proportion.
  • In the se_hat column, calculate the standard error of X_hat for each poll using the sqrt function.
  • In the lower column, calculate the lower bound of the 95% confidence interval using the qnorm function.
  • In the upper column, calculate the upper bound of the 95% confidence interval using the qnorm function.
  • Use the select function to select the columns from polls to save to the new object pollster_results.