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3. The starting point i.e the lower limit of the first class,
should either be zero or 5 or multiple of 5.
4. To ensure continuity and to get correct class interval we
should adopt “exclusive” method.
5. Wherever possible, it is desirable to use class interval of
equal sizes.
56 4.6 Preparation of frequency table:
The premise of data in the form of frequency distribution
describes the basic pattern which the data assumes in the mass.
Frequency distribution gives a better picture of the pattern of data if
the number of items is large. If the identity of the individuals about
whom a particular information is taken, is not relevant then the first
step of condensation is to divide the observed range of variable
into a suitable number of classintervals and to record the number
of observations in each class. Let us consider the weights in kg of
50 college students.
42 62 46 54 41 37 54 44 32 45
47 50 58 49 51 42 46 37 42 39
54 39 51 58 47 64 43 48 49 48
49 61 41 40 58 49 59 57 57 34
56 38 45 52 46 40 63 41 51 41
Here the size of the class interval as per sturges rule is obtained as
follows
Range
Size of class interval = C =
1+3.322 logN
64  32
32
=
=
5
1+3.322 log(50)
6.64
Thus the number of class interval is 7 and size of each class
is 5. The required size of each class is 5. The required frequency
distribution is prepared using tally marks as given below:
Class Interval
Tally marks
Frequency
3035
2
3540
6
4045
12
4550
14
5055
6
5560
6
6065
4
Total
50
57 Example 2:
Given below are the number of tools produced by workers in a
factory.
43
40
34
33
28
31
32
23
21
22 18
25
18
39
44
19
20
20
26
45
38
25
13
14
27
41
42
17
31
32
27
33
37
25
26
32
25
34
35
46
29
34
31
34
35
24
30
41
32
29
28
30
31
30
34
35
36
29
26
32
36
35
36
37
23
22
29
33
37
33
27
24
36
42
29
37
29
23
44
41
45
39
21
42
22
28
22
15
16
17
28
29
35
31
27
40
23
32
40
37
Construct frequency distribution with inclusive type of class
interval. Also find.
1. How many workers produced more than 38 tool...
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This note was uploaded on 01/18/2014 for the course BUS 100 taught by Professor Moshiri during the Winter '08 term at UC Riverside.
 Winter '08
 Moshiri
 Business

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