8
Chapter 1
0 10
Figure 1.1
sample size.
|
|
|
I
20 30 40 50
60 70 80
Stress, ksi
Mean, # and standard deviation a or ~ for 95% confidence and infinite
substituting
8334~
2.2405 - - 0.0313
525.8 psi < ~r < 37,631 psi
Now sketch the values in (Fig. 1.1). As it will be seen, some features will
present contradictions
Note from Fig. 1.1
/~ - 3s = negative values for most of the final results.
Ifa design allowable is picked for N= 2 the approach in Eq. (1.24) and Fig.
1.1 for 95% confidence
c~ = Yc - Ks
(1.32)
A-basis 99% of values greater than c~A with K= 37.094 (Table E.1)
B-basis 90% of values greater than c~ with K=20.581 (Table E.1)
C~A = 42,500--37.094 (833) = 11,600 psi for 2 values
~=42,500--20.581 (833)=25,356 psi for ~ values
This is better but still not great. An approach [1.8] will be attempted using
Table E.6. Average of best two
# = 1/2(xl + x2) = 1/2(40,000 + 45,000) = 42.500
(1.33)
Chapter 1
0 10
Figure 1.1
sample size.
|
|
|
I
20 30 40 50
60 70 80
Stress, ksi
Mean, # and standard deviation a or ~ for 95% confidence and infinite
substituting
8334~
2.2405 - - 0.0313
525.8 psi < ~r < 37,631 psi
Now sketch the values in (Fig. 1.1). As it will be seen, some features will
present contradictions
Note from Fig. 1.1
/~ - 3s = negative values for most of the final results.
Ifa design allowable is picked for N= 2 the approach in Eq. (1.24) and Fig.
1.1 for 95% confidence
c~ = Yc - Ks
(1.32)
A-basis 99% of values greater than c~A with K= 37.094 (Table E.1)
B-basis 90% of values greater than c~ with K=20.581 (Table E.1)
C~A = 42,500--37.094 (833) = 11,600 psi for 2 values
~=42,500--20.581 (833)=25,356 psi for ~ values
This is better but still not great. An approach [1.8] will be attempted using
Table E.6. Average of best two
# = 1/2(xl + x2) = 1/2(40,000 + 45,000) = 42.500
(1.33)