Question

• Write a function calculate_mean_ci(). • The inputs to this function are of the form (x, sigma, level). These are X: a numeric vector. sigma : population standard deviation. level : the confidence level given as a percentage, e.g., 95. • The output is a vector of length two of the form [lwr, upr), where MT lwr = ī – 20.025

Answer 1

R code with comments

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#the function to get the confidence interval
calculate_mean_ci<-function(x,sigma,level){
   #get the sample mean
   xbar<- mean(x)
   #get the sample size
   n<-length(x)
   #get the significance level
   alpha<-1-level/100
   #get the critical value
   z<- qnorm(1-alpha/2,0,1)
   #get the lower limit
   lwr<-xbar-z*sigma/sqrt(n)
   #get the upper limit
   upr<-xbar+z*sigma/sqrt(n)
   return(c(lwr,upr))
}

#test the function
x<-c(10,12,14,15,25,9,11,17,18)
calculate_mean_ci(x,5,95)
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get this

[1] 11.28895 17.82216