linear statistical models 2009 models for continuous, binary and binomial responses simple linear...
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Linear statistical models 2009
Models for continuous, binary and binomial responses
Simple linear models regarded as special cases of GLMs Simple linear regression
One-way ANOVA
Two-way ANOVA with or without interaction effects
Some useful continuous distributions
Binary and binomial responses
Linear statistical models 2009
A simple linear regression model
Heart rate in the common leopard frog
y = 1.775x + 2.1389
0
5
10
15
20
25
30
35
40
0 2 4 6 8 10 12 14 16 18 20
Temperature (oC)
Hea
rt r
ate
(b
ea
ts/m
inu
te)
r = 0.967
Temp. (oC) Heart rate (beats/min)2 5
4 116 118 14
10 2212 2314 32
16 2918 32
Linear statistical models 2009
GENMOD implementation of simple linear regression
proc genmod data=linear.heartrate;
model heart_rate = temp /dist=normal link=identity;
run;
Analysis of Parameter Estimates
Standard Wald 95% Confidence Chi-
Parameter DF Estimate Error Limits Square Pr > ChiSq
Intercept 1 2.1389 1.6906 -1.1746 5.4524 1.60 0.2058
Temp 1 1.7750 0.1502 1.4806 2.0694 139.63 <.0001
Scale 1 2.3271 0.5485 1.4662 3.6936
NOTE: The scale parameter was estimated by maximum likelihood.
Linear statistical models 2009
Comparison of GENMOD and
MINITAB’s simple linear regression
GENMOD Analysis of Parameter Estimates
Standard Wald 95% Confidence Chi-
Parameter DF Estimate Error Limits Square Pr > ChiSq
Intercept 1 2.1389 1.6906 -1.1746 5.4524 1.60 0.2058
Temp 1 1.7750 0.1502 1.4806 2.0694 139.63 <.0001
Scale 1 2.3271 0.5485 1.4662 3.6936
NOTE: The scale parameter was estimated by maximum likelihood.
MINITAB Regression Analysis: Heart_rate versus Temp
The regression equation is Heart_rate = 2.14 + 1.77 Temp
Predictor Coef SE Coef T P
Constant 2.139 1.917 1.12 0.301
Temp 1.7750 0.1703 10.42 0.000
S = 2.63869 R-Sq = 93.9% R-Sq(adj) = 93.1%
Linear statistical models 2009
Comparison of GENMOD and
MINITAB’s simple linear regression
The point estimates of the fitted line are identical
The deviance
in GENMOD is equal to the error sum of squares
The estimates of the standard deviation are different
The Wald-tests and the t-tests are different
22 ˆˆ n
pnML
));;ˆ();;((2 ylyylD
Linear statistical models 2009
One-way ANOVA
Zr_content Temperature Sample Hardness_Gpa1 400 1 29.929541 400 1 29.623641 400 1 26.294591 400 1 28.104281 400 1 30.176241 400 1 30.817871 400 1 27.204221 400 1 26.83581 400 1 28.967041 400 1 28.273511 400 1 21.927731 400 1 28.156741 400 1 30.616291 400 1 27.67011 400 1 29.910871 400 1 28.16759
Measurement of hardness for nine groups of samples (3 levels of Zr, 3 temperature levels)
Linear statistical models 2009
GENMOD implementation of one-way ANOVA
proc genmod data=linear.hardness;
class zr_content temperature sample;
model hardness_Gpa = sample /dist=normal link=identity;
run;
Analysis Of Parameter Estimates
Standard Wald 95% Confidence Chi- Parameter DF Estimate Error Limits Square Pr > ChiSq
Intercept 1 35.9016 0.4357 35.0476 36.7555 6789.78 <.0001 Sample 1 1 -6.8011 0.6130 -8.0024 -5.5997 123.11 <.0001 Sample 2 1 -6.8303 0.6195 -8.0446 -5.6161 121.56 <.0001 Sample 3 1 -8.1457 0.6130 -9.3471 -6.9443 176.61 <.0001 Sample 4 1 -13.4144 0.6195 -14.6286 -12.2002 468.86 <.0001 Sample 5 1 -8.6257 0.4800 -9.5665 -7.6850 322.95 <.0001 Sample 6 1 -10.4443 0.6099 -11.6396 -9.2490 293.30 <.0001 Sample 7 1 -8.5459 0.6162 -9.7535 -7.3382 192.36 <.0001 Sample 8 1 -3.1868 0.6565 -4.4735 -1.9001 23.56 <.0001 Sample 9 0 0.0000 0.0000 0.0000 0.0000 . . Scale 1 2.9870 0.0871 2.8211 3.1627 NOTE: The scale parameter was estimated by maximum likelihood.
Linear statistical models 2009
GENMOD implementation of one-way ANOVA
Standard Wald 95% Confidence Chi-GENMOD Parameter DF Estimate Error Limits Square Pr > ChiSq
Intercept 1 35.9016 0.4357 35.0476 36.7555 6789.78 <.0001 Sample 1 1 -6.8011 0.6130 -8.0024 -5.5997 123.11 <.0001 Sample 2 1 -6.8303 0.6195 -8.0446 -5.6161 121.56 <.0001 Sample 3 1 -8.1457 0.6130 -9.3471 -6.9443 176.61 <.0001 Sample 4 1 -13.4144 0.6195 -14.6286 -12.2002 468.86 <.0001 Sample 5 1 -8.6257 0.4800 -9.5665 -7.6850 322.95 <.0001 Sample 6 1 -10.4443 0.6099 -11.6396 -9.2490 293.30 <.0001 Sample 7 1 -8.5459 0.6162 -9.7535 -7.3382 192.36 <.0001 Sample 8 1 -3.1868 0.6565 -4.4735 -1.9001 23.56 <.0001 Sample 9 0 0.0000 0.0000 0.0000 0.0000 . . Scale 1 2.9870 0.0871 2.8211 3.1627MINTAB ANOVA Pooled StDev
Level N Mean StDev ------+---------+---------+---------+---
1 48 29.100 2.770 (-*-)
2 46 29.071 2.605 (--*-)
3 48 27.756 1.777 (-*--)
4 46 22.487 2.842 (-*-)
5 220 27.276 2.699 (*)
6 49 25.457 3.385 (-*-)
7 47 27.356 4.465 (-*--)
8 37 32.715 3.815 (--*-)
9 47 35.902 3.236 (-*-)
------+---------+---------+---------+---
24.0 28.0 32.0 36.0
Pooled StDev = 3.010
Linear statistical models 2009
GENMOD implementation of two-way ANOVA
proc genmod data=linear.hardness;
class zr_content temperature sample;
model hardness_Gpa = zr_content temperature zr_content * temperature/dist=normal link=identity;
run;
Analysis Of Parameter Estimates
Standard Wald 95% Confidence Chi-
Parameter DF Estimate Error Limits Square Pr > ChiSq
Intercept 1 27.7559 0.4311 26.9108 28.6009 4144.59 <.0001
Zr_content 0.17 1 8.1457 0.6130 6.9443 9.3471 176.61 <.0001
Zr_content 0.5 1 -2.2986 0.6066 -3.4875 -1.1097 14.36 0.0002
Zr_content 1 0 0.0000 0.0000 0.0000 0.0000 . .
Temperature 400 1 1.3446 0.6097 0.1496 2.5397 4.86 0.0274
Temperature 800 1 1.3154 0.6163 0.1074 2.5233 4.56 0.0328
Temperature 1000 0 0.0000 0.0000 0.0000 0.0000 . .
Zr_conten*Temperatur 0.17 400 1 -9.8905 0.8668 -11.5895 -8.1915 130.18 <.0001
Zr_conten*Temperatur 0.17 800 1 -4.5022 0.9004 -6.2670 -2.7373 25.00 <.0001
Zr_conten*Temperatur 0.17 1000 0 0.0000 0.0000 0.0000 0.0000 . .
Zr_conten*Temperatur 0.5 400 1 -4.3147 0.8648 -6.0096 -2.6199 24.90 <.0001
Zr_conten*Temperatur 0.5 800 1 0.5032 0.7762 -1.0181 2.0245 0.42 0.5168
Zr_conten*Temperatur 0.5 1000 0 0.0000 0.0000 0.0000 0.0000 . .
Zr_conten*Temperatur 1 400 0 0.0000 0.0000 0.0000 0.0000 . .
Zr_conten*Temperatur 1 800 0 0.0000 0.0000 0.0000 0.0000 . .
Zr_conten*Temperatur 1 1000 0 0.0000 0.0000 0.0000 0.0000 . .
Scale 1 2.9870 0.0871 2.8211 3.1627
Linear statistical models 2009
The gamma distribution
Expected value:
Variance: 2
)/exp()(
1),;( 1
yyyf
0
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0 10 20 30 40 50
Den
sity
fu
nct
ion
Linear statistical models 2009
The 2 distribution
Expected value: p
Variance: 2p
Special case of gamma distribution
Sum of independent squared standard normal distributions
)2/exp(2)2/(
1);( 1)2/(
2/yy
ppyf p
p
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0 10 20 30 40 50
Den
sity
fu
nct
ion
Linear statistical models 2009
A model of the mean of a gamma distribution
proc genmod data=linear.clottingtime;
model clotting_time = lconc agent lconc * agent/dist=gamma link=power(-1) residuals;
output out=linear.clottingout resdev=resdev pred=pred;
run;
Conc Lconc Agent Clotting_time5 1.61 1 11810 2.30 1 5815 2.71 1 4220 3.00 1 3530 3.40 1 2740 3.69 1 2560 4.09 1 2180 4.38 1 19100 4.61 1 185 1.61 0 6910 2.30 0 3515 2.71 0 2620 3.00 0 2130 3.40 0 1840 3.69 0 1660 4.09 0 1380 4.38 0 12100 4.61 0 12
Linear statistical models 2009
Binary and binomial responses
The response probabilities are modelled as functions of
the predictors
Link functions:
the probit link:
the logit link:
the log-log link:
p
pplogit
1log)(
)()( 1 ppprobit
))1log(log()( ppCL