If in a grouped frequency distribution, the classes are 20 - 30, 30 - 40, 40 - 50, …, then the observation 40 is included in the class :

1. 30 - 40

2. 40 - 50

3. 50 - 60

4. 20 - 30

If in a grouped frequency distribution, the class intervals are 20 - 29, 30 - 39, 40 - 49, …., then the observation 29.4 is included in the class :

1. 20 - 29

2. 30 - 39

3. 40 - 49

4. 29 - 30

In a grouped frequency distribution, the class interval are 40 - 49, 50 - 59, …, 80 - 89. The upper boundary of the class (50 - 59) is :

1. 59

2. 59.5

3. 49.5

4. 60

If 0 - 9, 10 - 19, 20 - 29, …., are the classes of a grouped frequency distribution, then the width of each class is :

1. 9

2. 9.5

3. 10

4. 9 or 10