266
Appendix E
Table E.6 Several estimates of the mean (variance to be multiplied by 2)
Median
Midrange
Mean of best two
N Var.
Eft.
Var.
Eft.
Statistic
Var.
Eft.
(x: +x3 + ...
+ XN_I)/(N-2)
Var.
Eft.
2 0.500
1.000 0.500 1.000 ½(XI+X2) 0.500
1.000
3 0.449
0.743 0.362 0.920 ½(XI+X3) 0.362
0.920 0.449
0.743
4 0.298
0.838 0.298 0.838 ½(X2+X3) 0.298
0.838 0.298
0.838
5 0.287
0.697 0.261 0.767 ½(X2+X4) 0.231
0.867 0.227
0.881
6 0.215
0.776 0.236 0.706 ½(X;+Xs) 0.193
0.865 0.184 0.906
7 0.210
0.679 0.218 0.654 ½(X2+X6) 0.168
0.849 0.155 0.922
8 0.168
0.743 0.205 0.610 ½(X3+X6) 0.149
0.837 0.134 0.934
9 0.166
0.669 0.194 0.572 ½(X3+XT) 0.132
0.843 0.118 0.942
10 0.138
0.723 0.186 0.539 ½(X3+Xs) 0.119
0.840 0.105 0.949
11 0.137
0.663 0.178 0.510 ½(X3+Xg) 0.109
0.832 0.0952 0.955
12 0.118
0.709 0.172 0.484 ½(X4+Xg) 0.100
0.831 0.0869 0.959
13 0.117
0.659 0.167 0.461 ½(X4+X~0) 0.0924 0.833 0.0799 0.963
14 0.102
0.699 0.162 0.440 ½(X4+XI=) 0.0860 0.830 0.0739 0.966
15 0.102
0.656 0.158 0.422 ½(X4+X~)0.0808
0.825 0.0688 0.969
16 0.0904 0.692 0.154 0.392 ½(Xs+X~2)0.0756
0.827 0.0644 0.971
17 0.0901 0.653 0.151 0.389 ½(Xs+X~3) 0.0711 0.827 0.0605 0.973
18 0.0810 0.686 0.148 0.375 ½(Xs+XI4) 0.0673 0.825 0.0570 0.975
19 0.0808 0.651 0.145 0.362 ½(X6+XI4) 0.0640 0.823 0.0539 0.976
20 0.0734 0.681 0.143 0.350 ½(X6+XIS) 0.0607 0.824 0.0511 0.978
o~ 1.57/N 0.637
0.000 ½(P25+P15) 1.24/N 0.808
1.000
Tables E.5 and E.6 are reproduced with permission of the McGraw-Hill Companies from
Wilffid J. Dixon and Frank J. Massey Jr., Introduction to Stat&tical Analys&, 3rd Edn,
McGraw-Hill Book Company, 1969, p. 488.
Appendix E
Table E.6 Several estimates of the mean (variance to be multiplied by 2)
Median
Midrange
Mean of best two
N Var.
Eft.
Var.
Eft.
Statistic
Var.
Eft.
(x: +x3 + ...
+ XN_I)/(N-2)
Var.
Eft.
2 0.500
1.000 0.500 1.000 ½(XI+X2) 0.500
1.000
3 0.449
0.743 0.362 0.920 ½(XI+X3) 0.362
0.920 0.449
0.743
4 0.298
0.838 0.298 0.838 ½(X2+X3) 0.298
0.838 0.298
0.838
5 0.287
0.697 0.261 0.767 ½(X2+X4) 0.231
0.867 0.227
0.881
6 0.215
0.776 0.236 0.706 ½(X;+Xs) 0.193
0.865 0.184 0.906
7 0.210
0.679 0.218 0.654 ½(X2+X6) 0.168
0.849 0.155 0.922
8 0.168
0.743 0.205 0.610 ½(X3+X6) 0.149
0.837 0.134 0.934
9 0.166
0.669 0.194 0.572 ½(X3+XT) 0.132
0.843 0.118 0.942
10 0.138
0.723 0.186 0.539 ½(X3+Xs) 0.119
0.840 0.105 0.949
11 0.137
0.663 0.178 0.510 ½(X3+Xg) 0.109
0.832 0.0952 0.955
12 0.118
0.709 0.172 0.484 ½(X4+Xg) 0.100
0.831 0.0869 0.959
13 0.117
0.659 0.167 0.461 ½(X4+X~0) 0.0924 0.833 0.0799 0.963
14 0.102
0.699 0.162 0.440 ½(X4+XI=) 0.0860 0.830 0.0739 0.966
15 0.102
0.656 0.158 0.422 ½(X4+X~)0.0808
0.825 0.0688 0.969
16 0.0904 0.692 0.154 0.392 ½(Xs+X~2)0.0756
0.827 0.0644 0.971
17 0.0901 0.653 0.151 0.389 ½(Xs+X~3) 0.0711 0.827 0.0605 0.973
18 0.0810 0.686 0.148 0.375 ½(Xs+XI4) 0.0673 0.825 0.0570 0.975
19 0.0808 0.651 0.145 0.362 ½(X6+XI4) 0.0640 0.823 0.0539 0.976
20 0.0734 0.681 0.143 0.350 ½(X6+XIS) 0.0607 0.824 0.0511 0.978
o~ 1.57/N 0.637
0.000 ½(P25+P15) 1.24/N 0.808
1.000
Tables E.5 and E.6 are reproduced with permission of the McGraw-Hill Companies from
Wilffid J. Dixon and Frank J. Massey Jr., Introduction to Stat&tical Analys&, 3rd Edn,
McGraw-Hill Book Company, 1969, p. 488.