NuAgain Remediation Co.want to test if a new procedure they have developed for removing copper from water differs in effectiveness from the standard procedure they use.

a)[1 mark]What null hypothesis should they use?

b)[2 mark]What alternative hypothesis should they use? Explain why you think a one or two-sided test is most appropriate in this case.

For 11 prepared samples of known concentration the new method removes an average ofx= 12.5units of copper. The old procedure is known to remove an average of 10.2 units under the same conditions. The sample standard deviation was found to be s = 3.4

c)[3 marks]How many standard deviations away from the value predicted by the null hypothesis is the sample mean? Show your working.

d)[2 marks]Does the test statistic you calculated in part (c) follow a t or a z distribution. Explain your choice.

e)[2 marks]The p-value is calculated to be 0.049. Interpret what this means in the context of this scenario.