Question

5. The price of coffee has been steadily declining since October 2012. The International Coffee Organization (ICO) reported that the mean price for coffee in May 2013 was 126.96 U.S. cents/lb. A random sample of 34 days was obtained and the composite indicator for Brazilian Natural coffee was recorded for each. The sample mean was

x = 130.29 U.S. cents/lb.

Assume the population standard deviation is 8.6 U.S. cents/lb. Is there any evidence to suggest that the mean composite indicator for Brazilian Natural is greater than 126.96? Use

α = 0.05.

a) Give the value of the appropriate z_α or z_α/2. (Round your answer to four decimal places.)

b) Calculate the test statistic. (Round your answer to four decimal places.)

z =

Answer 1

a)

H0: <= 126.96

Ha: > 126.96

This is one (right ) tailed test.

Z = 1.6449

b)

Test statistics z = ( - ) / ( / sqrt(n) )

= (130.29 - 126.96) / (8.6 / sqrt(34)

= 2.2578

Since test statistics falls in rejection region (That is greater than 1.6449) , Reject H0.