I got 17 but I don\'t know how to used R code get 18. Show me the code if you ca

Question

I got 17 but I don't know how to used R code get 18.

Show me the code if you can or just normal calculate.

Thanks!

Use the Following Text for Questions 17-18 The average life of a bread-making machine is 7 years, with a standard deviation of 1 year. Assume that the lives of these machines follow approximately a normal distribution. Source: Walpole, RE. Mlyers, R H. Myers, S & Ye, K. 2012. Probabiliv Statistics for Engineers & Scientists. Bo MA: Pearson. ston, 17. Find the probability that the mean life of a random sample of 16 such machines falls between 6-8 and 7.3 years. You must show all work (includ ing R Code and output in order to receive full credit. (3 points) Mean u 7 years, Standard Deviation 1 year. size-16. ample mean 7 years Sampling standard deviation J 1/root 16 0.25 years pnormcz 2 means 7,sd 0. 25) -pnormC6. 8, mean 7 ,sd 0. 25) [1] 0.5762892 Answer 0.5763 18. Find the value of x to the right of which 20% of the means computed from random samples of size 16 would fall. You must show all work (including R Code and output in order to receive full credit. 3 points)

Explanation / Answer

Given X follows N(7,1) distribution. Sample size n=16, sample mean=7 years and sample standard deviation = 0.25

18. Find X such that 20% of the means computed from random sample of size 16 would fall to right of it. It means

P(X >x) =0.20 ==> P(X <= x) =1-0.20= 0.80

R code to find X is

> qnorm(0.80,7,0.25)
[1] 7.210405

So for x=7.21 20% of the means would fall right side.

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