Use R studio script to solve the problem

set.seed(2024) kickstarter_data <- read.csv("ks-projects-201801.csv") head(kickstarter_data)

Suppose you are interested in the variable "usd_pledged_real", please use each "main_category" as the stratum and the proportional allocation principle to get a stratified sample with size around 5000 (round the number of sampled units in each stratum to the nearest integer). Estimate the population average and its standard deviation.