Solution :
Class Frequency Class boundaries Mid Relative Cumulative
point frequency frequency
1132-1191 5 1131.5-1191.5 1161.5 0.2381 5
1192-1251 3 1191.5-1251.5 1221.5 0.1428 8
1252-1311 2 1251.5-1311.5 1281.5 0.0952 10
1312-1371 5 1311.5-1371.5 1341.5 0.2381 15
1371-1431 4 1371.5-1431.5 1401.5 0.1905 19
1432-1491 2 1431.5-1491.5 1416.5 0.0952 21
Total 21
Therefore, the lower class boundary for the sixth class is 1431.5