NCERT Solutions for Class 9 Maths Chapter 14 Statistics

Short Note:

• Primary data is collected by the investigator directly; secondary data is collected by someone else and used by the investigator.

• Raw data can be organised into a frequency distribution table, grouping observations into class intervals with their frequencies.

Short Note:

• Bar Graph: a display using bars of uniform width, with heights proportional to the corresponding frequencies/values, for discrete categories.

• Histogram: a graph for continuous class intervals, drawn as adjacent rectangles with no gaps (unless class sizes vary, requiring adjusted heights).

• Frequency Polygon: obtained by joining the mid-points of the tops of the rectangles of a histogram with straight lines.

Short Note:

• Mean (average) = sum of all observations ÷ number of observations.

• Median: the middle-most observation when data is arranged in order; for even n, average of the two middle values.

• Mode: the observation that occurs most frequently in the data.