What are primary data and secondary data ? Which of the two are more reliable and why?

Fill in the blanks

(i) The difference between the maximum and minimum observations in a data is called the ………… of the data.

(ii) The number of observations in a class-interval is called the ………… of the interval.

(iii) The mid-point of a class-interval is called the ………… of the interval.

(iv) Lower-limit of the class-interval 24-30 is …………

(v) Upper limit of the class-interval 16-20 is …………

(vi) The class-mark of the class-interval is 20-30 is …………

(vii) The class-mark of the class-interval 9.5-19.5 is …………

Find the range of the data

(a) 5, 7, 16, 21, 8, 10

(b) 11, 13, 17, 14, 19, 14, 15, 18

The class marks of a frequency distribution are 28, 34, 40, 46, 52. Find the class-size and all the class intervals.