An environmental scientist investigates whether a seasonal upwelling event changes the pH level of seawater at various coral reef locations. The pH levels are measured before and after the upwelling. After excluding locations that showed no change in pH, a Sign Test is conducted on the differences with a sample size of $N = 11$ . The calculated test statistic is found to be $S = 2$ .

Using Table 1, explain whether or not there is a significant difference in pH levels at the 0.05 level of significance for a two-tailed test.

Table 1: Critical values of $S\,$ for the Sign Test

$N$	Level of significance for a two-tailed test
	0.10	0.05	0.01
8	1	0	-
9	1	1	0
10	1	1	0
11	2	1	0
12	2	2	1
13	3	2	1

Note: Significance is shown if the calculated value of $S\,$ is equal to or less than the critical value.

Using Table 1, explain whether or not there is a significant difference in pH levels at the 0.05 level of significance for a two-tailed test.

Table 1: Critical values of $S\,$ for the Sign Test

$N$	Level of significance for a two-tailed test
	0.10	0.05	0.01
8	1	0	-
9	1	1	0
10	1	1	0
11	2	1	0
12	2	2	1
13	3	2	1

Note: Significance is shown if the calculated value of $S\,$ is equal to or less than the critical value.

Inferential testing (A-level only)

Question 8

Table 1: Critical values of $S\,$ for the Sign Test

Markscheme

Inferential testing (A-level only)

Question 8

Table 1: Critical values of $S\,$ for the Sign Test

Markscheme

Inferential testing (A-level only)

Question 8

Table 1: Critical values of S S\,S for the Sign Test

Inferential testing (A-level only) Questions

Inferential testing (A-level only)

Question 8

Table 1: Critical values of S S\,S for the Sign Test

Inferential testing (A-level only) Questions

Table 1: Critical values of $S\,$ for the Sign Test

Table 1: Critical values of $S\,$ for the Sign Test