A researcher working for a drug company is interested in investigating the effect of storage on the potency of one of the company's drugs. 10 freshly produced bottles of the drug are randomly selected and the potency measured. Another 10 freshly produced bottles of the drug are randomly chosen and stored under controlled conditions for 6 months before the potency was measured. Summary statistics are displayed below:

(a) Carry out a t-test to investigate if there is a difference between the underlying mean potency for freshly produced drugs and that of drugs stored for 6 months. Notes:

(i) Refer to the instructions on page 1 of this assignment: "Hypothesis tests in this assignment".

(ii) Follow the step-by-step guide to performing a t-test

(iii) Once you have calculated your test statistic, it is necessary to use either a graphics calculator, SPSS, Excel or t-tables to determine the P-value.

(b) Does your confidence interval from part (a) contain the true difference? Briefly explain.