Question 7: Combined spread across poll type

Calculate the confidence intervals of the spread combined across all polls injune_polls, grouping by poll type. Recall that to determine the standard error of the spread, you will need to double the standard error of the estimate.

Use this code (which determines the total sample size per poll type, gives each spread estimate a weight based on the poll's sample size, and adds an estimate of p from the combined spread) to begin your analysis:

combined_by_type <- june_polls %>%

group_by(poll_type) %>%

summarize(N = sum(samplesize),

spread = sum(spread*samplesize)/N,

p_hat = (spread + 1)/2)

What is the lower bound of the 95% confidence interval for online voters?