The class-mark of a class interval is 42. If the class-size is 10, then the upper and lower limits of the class are

1. 47 and 37

2. 47.5 and 37.5

3. 46.5 and 36.5

4. 46 and 36

The following marks were obtained by the students in a test :

81, 72, 90, 90, 86, 85, 92, 70, 71, 83, 89, 95, 85, 79, 62.

The range of marks is :

1. 9

2. 17

3. 27

4. 33

Let L be the lower class boundary of a class in a frequency distribution and m be the mid-point of the class. Which of the following is the upper boundary of the class?

1. m + $\dfrac{\text{m + L}}{2}$

2. L + $\dfrac{\text{m + L}}{2}$

3. 2m - L

4. m - 2L

A frequency polygon is constructed by plotting frequency of the class interval and the :

1. upper limit of the class

2. lower limit of the class

3. either (a) or (b)

4. mid-value of the class