⇒ The three measures of central tendency are:
⇒ Mean can be calculated by the following methods:
(a) Direct Method
(b) Short-cut Method
(c) Step Deviation Method
⇒ The mean can be calculated by the following formulae :
where A = assumed mean and di = xi - A
⇒ The median of the distribution is the middle value of a distribution.
⇒ The median of a grouped frequency distribution can be calculated by:
l = lower limit of median class
l = frequency of median class
h = width of median class
c.f. = cumulative frequency of the class preceding the median class.
⇒ Mode is the value of the variable which has the maximum frequency.
⇒ The mode of a continuous frequency distribution may be computed by the following formulae:
l = lower limit of the modal class.
f1 = frequency of modal class.
f2 = frequency of class succeeding the modal class.
fo = frequency of class preceding the modal class.
h = size of the class interval.
⇒ The relation between the three measures of central tendency is
Mode = 3 Median - 2 Mean OR 3 Median = Mode + 2 Mean.
⇒ Ogives are used to get the median of a frequency distribution