Key Points - Statistics

1. Collection of Data
2. Presentation of Data
3. Graphical Representation of Data
4. Measures of Central Tendency

- Statistics is the area of study that deals with the collection presentation. analysis and interpretation of data.
- Data: Facts or figures. collected with a definite purpose. are called data.
- There are two types of data (i) Primary (ii) Secondary
- We can represent the data by (i) ungrouped and grouped frequency distribution.
- Data can also represent by (i) bar graph (ii) Histogram (iii) Frequency polygons
- Class mark of grouped data is
- Measure of central tendencies by mean. median. mode.
- Mean: (x) = sum of all observations / Total no. of observations
- If observations denoted by and their occurrence i.e. frequency is denoted by then mean is (x) =
 Σlower lim it + upper lim it  (x) = Σfixi / Σfi
 

- Median: Arrange the observations in ascending or descending order then if numbers of observations (n) are odd then then median is + 2 term.
If no. of observations (n) are even. then median is average of 1/2 + n/2 + terms.

- Mode: The observation whose frequency is greatest.
- Mode = 3 median - 2 mean.