This question was reportedly attempted by majority of the candidates and their performancewas described as fair. However, it was observed that some candidates calculated the mean without using the assumed mean. This was wrong as they were expected to use the assumed mean. Some others were reported not to manipulate the decimals involved correctly.
Candidates were expected to obtain the following table:
Length 
f 
Class midpoint (x) 
d=xa 
fd 
1.0 1.1 
2 
1.05 
 0.4 
 0.8 
1.2 – 1.3 
3 
1.25 
 0.2 
 0.6 
1.4 1.5 
8 
1.45 
0.0 
0.0 
1.6 1.7 
5 
1.65 
0.2 
1.0 
1.8 1.9 
2 
1.85 
0.4 
0.8 

∑f = 20 


∑fd = 0.4 
Using the table, the mean would be calculated using the formula,
mean = A+ , where A = assumed mean = 1.45, ∑fd = 0.4 and ∑f = 20. Therefore, mean = 1.45 +