Class 7 NCERT

Data - collection of numerical figures
types of data
- Primary - collected by a person directly
- Secondary - obtained from published or unpublished sources
Organisation of data
- Raw data - collected and put in without any arrangements
- Array - put in ascending or descending order
- Tabulation - in form of a table
- Observation - Each numerical figure in a data
- Frequency - number of times the data occurs
- Frequency distribution - table format to present the data to easily understand
Tally marks
Representative or central value:
- arithmetic mean
- median
- mode
Mean: (x bar)
- = sum of all observations / number of observation
Range:
- = value of greatest observation - value of smallest observation
Mode:
- value of the observation that occurs more frequently
Median:
- value that divides the group into 2 equal parts
- arrange the data in ascending or descending order
- determine the total number of observations - n
- if n is odd, = (n+1) / 2 observation
- if n is even, = (n/2) + (n+1 / 2) observation

Mode = 3 Median - 2 Mean

Construction of bar graph:
- draw the x and y axis
- write the title for the axis
- choose the scale
- draw the bars
Probability
- probability of random event
- impossible & possible event

Class 7 - Arjun