Which (if any) of the following statements about hypothesis testing is CORRECT?

A. With a large sample size you will always calculate a large P‐value from your hypothesis test.

B. The P‐value from a hypothesis test is the probability of obtaining your results, or more extreme results, if the null hypothesis were true.

C. With a small sample size you will always calculate a small P‐value from your hypothesis test.

D. The P‐value from a hypothesis test tells you what the difference is and how large the difference is.

E. A statistically significant result means the result is clinically significant/practically important.

Farndon et al. (2013) report the results of a randomised controlled trial that investigated the effectiveness of salicylic acid plasters (Corn plasters) compared with usual scalpel debridement for treatment of foot corns. One of the secondary outcome measures was the size of the index corn (in mm) measured at 3, 6, 9 and 12 months postrandomisation.

Table

 6.4 shows the outcome data.

You may assume a significance level of 0.05 or 5% has been specified for the various hypothesis tests.

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Table 6.4 Index corn size, in millimetres, over time by group. Corn plaster Scalpel Size of (n = index (n = Mean 101) 101) 95% CI corn Mean SD Mean SD Difference Lower Upper P-value (mm) Baseline 3.9 (1.7) 3.8 (1.8) 3 1.7 (1.5) 2.7 (2.3) -1.0 -1.5 -0.5 months 6 1.7 (1.6) 2.4 (2.2) -0.7 -1.2 -0.2 months 9 1.7 (1.6) 2.2 (2.1) -0.5 -1.2 0.1 months 12 1.3 (1.6) 2.3 (2.2) -1.0 -1.7 -0.2 0.010 months