P3 Exam December 2013 – Question 2

Dear Sir,

There is one paragraph in the answers of Question 2 that I could not understand:

Using a ‘best guess’ approach, a trend value of 149 might be hypothesised for quarter 1 of 2013, giving a predicted value of 134·3 (149 – 14·7), just below the actual recorded value of 137. Predicted values would also be calculated for subsequent quarters. For example,
based on a (hand drawn) trend value of 151, the predicted value for quarter 3 of 2013 would be 173·55 (151 + 22·55), which subjectively seems much more realistic than the 152·55 suggested by the least squares analysis.

Could you provide a more detailed explaination what basis for the statement of “based on a (hand drawn) trend value of 151”. I could not firgue out why they choose 151.

Thanks in advance.