What is the mean 1 mile running time over 18 weeks?

Health Promotion

A man runs 1 mile approximately once per weekend. He records his time over an 18-week period. The individual times and summary statistics are given in Table 2.14.

Table 2.14:One mile running time for an individual, over 18 weeks

Time (min)(x,) Time (min)(x,) WK WK 12.80 11.57 10 12.20 11 11.73 12 3 12.25 12.67 4 12.18 13 11.92 11.53 14 11.67 11.80 12.47 15 12.30 16 12.33 8. 12.08 17 12.55 11.72 18 11.83