Chap 14 Statistics

What is Statistics ?

Collection

Presentation

Analysis

Conclusion

GROUPED FREQUENCY DISTRIBUTION TABLE

Classes

Frequency

0 - 10

10 - 20

20 - 30

30 - 40

5

7

10

8

CLASSES ARE OF TWO TYPES

Discontinuous Classes

Continuous Classes

For e.g. :

1 - 10

11 - 20

21 - 30

0 - 10

10 - 20

20 - 30

For e.g. :

0.5 – 10.5

10.5 – 20.5

20.5 – 30.5

Lets convert discontinuous class into continuous

To convert discontinuous to continuous classes there are two steps-

1) Find x = (difference between consecutive lower and upper limits) ÷ 2

2) Subtract (x) from the lower limit and add (x) to upper limit of every class in the given set of Discontinuous Classes

1 – 0.5 = 0.5

10 + 0.5 = 10.5

11 – 0.5 = 10.5

20 + 0.5 = 20.5

21 – 0.5 = 20.5

30 + 0.5 = 30.5

25

15

5

Now we will learn to find Class mark or Midpoint of a class.

Class Mark

Lower limit + Upper limit

2

=

It is denoted as x _i in the entire chapter.

Class

Class Mark

1 - 10

11 - 20

21 - 30

5.5

15.5

25.5

Class

Class Mark

0 - 10

10 - 20

20 - 30

Class width (h) is found by subtracting two consecutive lower limits or

two consecutive upper limits.

Class width (h) can also be found by subtracting two consecutive Class marks.

Also if we add class width (h) to one class mark we get the next class mark .