F. K. Kong MA, MSc, PhD, CEng, FICE, FIStructE, R. H. Evans CBE, DSc, D ès Sc, DTech, PhD, CEng, FICE, FIMechE, FIStructE (auth.)-Reinforced and Prestressed Concrete-Springer US (1987)

4 Limit state design concepts
Table 1.3-2 Frequency distribution
Class interval
1.45-1.54
1.55-1.64
1.65-1.74
1.75-1.84
1.85-1.94
1.95-2.04
2.05-2.14
2.15-2.24
2.25-2.34
2.35-2.44
2.45-2.54
2.55-2.64
2.65-2.74
Frequency
/;
2
4
9
15
11
23
6
12
7
6
3
1
1
of different magnitudes are distributed over the range of the observed
values.
In Fig. 1.3-1 the frequency distribution is represented graphically as a
histogram. The principle of the histogram is that the area (not the ordinate)
of each rectangle represents the proportion of observations falling in that
interval. For example, the proportion of tensile strengths in the interval
1.45-1.54 N/mm 2 is 2/100 = 0.02, where 100 is the total number of test
results; this is represented in Fig. 1.3-1 by a rectangle of the same area,
namely, a rectangle of width 1 N/mm 2 and height 0.02 per N/mm 2 , erected
on the base 1.45-1.54 N/mm 2 . If the number of observations (i.e. the test
>.
u
c
Q.l
::J
0"
Q.l
tt 0·05
0
'!,
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ t!
.... .... cil c\1
.:- co ~ 0 .... N ~ ~ It)
I I I
th
"'
N N cil cil c:\1
I I I I I I I I I
It) It) It) It) It) It) It) It) It) It) It)
.... .... .... .... .... .... c\i c\1 c:\1 c\i c\i N c\i
~ ~ ct;> r:- co ~ 0 .... N rt) ~ 1.(1
:B
Fig. 1.3-1 Histogram