4. A doctor believes that the span of a person's dominant hand is greater than that of the weaker hand. To test this theory, the doctor measures the spans of the dominant and weaker hands of a random sample of 8 people. He subtracts the span of the weaker hand from that of the dominant hand. The spans, in mm , are summarised in the table below.
| \(A\) | \(B\) | \(C\) | \(D\) | \(E\) | \(F\) | \(G\) | \(H\) |
| Dominant hand | 202 | 251 | 215 | 235 | 210 | 195 | 191 | 230 |
| Weaker hand | 195 | 249 | 218 | 234 | 211 | 197 | 181 | 225 |
Test, at the 5\% significance level, the doctor's belief.
(9)