description
- Mean , Median , Mode
- Quartile , Inter quartile
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The three measures of central tendency for ungrouped data are :
The mean (or average) of a number of observations is the sum of the values of all the observations divided by the total number of observations.
So, `bar x =
(sum_(i=1)^n x_i)/ n`.
For an ungrouped frequency distribution, it is `bar x = (sum_(i=1)^n f_ix_i)/(sum_(i=1)^n f_i)`
The median is that value of the given number of observations, which divides it into exactly two parts.
If n is an odd number, the median = value of the `((n + 1)/2)^(th)` observation.
If n is an even number, median = Mean of the values of the `(n/2)^(th)` and `(n/2 + 1)^(th)` observation.
The mode is that value of the observation which occurs most frequently, i.e., an observation with the maximum frequency is called the mode.
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Candidates of four schools appear in a mathematics test. The data were as follows:
| Schools | No. of candidates |
Average score |
| 1 | 60 | 75 |
| 2 | 48 | 80 |
| 3 | N A | 55 |
| 4 | 40 | 50 |
If the average score of the candidates of all the four schools is 66, find the number of
candidates that appeared from school 3.
Find the missing value of p for the following distribution whose mean is 12.58.
| x | 5 | 8 | 10 | 12 | p | 20 | 25 |
| f | 2 | 5 | 8 | 22 | 7 | 4 | 2 |
