CLASS 9 / MATHS / STATISTICS / points to remember

CHAPTER – 14

STATISTICS

Points to remember:

1.   STATISTICS : It is a branch of science which deals with the collection, presentation, analysis and interpretation of numerical data.

2.   DATA : Facts or numerical figures, collected with a definite purpose, are called data.

3.   Data can be classified into two types depending upon ‘how the information is being collected’

A) PRIMARY DATA

B) SECONDRY DATA

4.  Data can be represented by the following ways

A) UNGROUPED FREQUENCY DISTRIBUTION TABLE

B) GROUPED FREQUENCY DISTRIBUTION TABLE (CONTINOUS / DISCONTINOUS)

5.  RANGE = HIGHEST VALUE – LOWEST VALUE.

6.  Graphically data can be represented by:

A) BAR GRAPH

B) HISTOGRAM

C) FREQUENCY POLYGON

7.   Three measures of central tendency of ungrouped data are: (i) mean, (ii) median and (iii) mode.

8.   MEAN : The mean of ungrouped data is found by adding all the values of observation and dividing it by the total number of observations. It is denoted by

9.   MEDIAN : The median is the value of the middlemost observation.

10 .MODE : The mode is the most frequently occuring observation.

If the number of observations ‘n’ is odd, then