Results: basicsenic.sas

Study of the Effectiveness of Nosocomial Infection Control

Elementary tests on the SENIC Data

Use proc freq to do crosstabs with chisquare test

The FREQ Procedure

The FREQ Procedure

Table region * medschl

Cross-Tabular Freq Table

Frequency
Expected
Row Pct
Table of region by medschl
region(Region of country (usa)) medschl(Medical school affiliation)
N Y Total
Northeast
23
24.743
79.31
6
4.2569
20.69
29
 
 
North Central
24
25.596
80.00
6
4.4037
20.00
30
 
 
South
32
29.009
94.12
2
4.9908
5.88
34
 
 
West
14
13.651
87.50
2
2.3486
12.50
16
 
 
Total
93
16
109
Frequency Missing = 4

Statistics for Table of region by medschl

Chi-Square Tests

Statistic DF Value Prob
WARNING: 50% of the cells have expected counts less
than 5. Chi-Square may not be a valid test.
Chi-Square 3 3.6761 0.2986
Likelihood Ratio Chi-Square 3 4.0646 0.2546
Mantel-Haenszel Chi-Square 1 2.0392 0.1533
Phi Coefficient   0.1836  
Contingency Coefficient   0.1806  
Cramer's V   0.1836  

Effective Sample Size = 109
Frequency Missing = 4

The TTEST Procedure

Prob of acquiring infection in hospital


Study of the Effectiveness of Nosocomial Infection Control

Elementary tests on the SENIC Data

T-test: Less risk at Hospitals with Med School Affiliation?

The TTEST Procedure

Variable: infrisk (Prob of acquiring infection in hospital)

Statistics

medschl N Mean Std Dev Std Err Minimum Maximum
N 89 4.2438 1.3434 0.1424 1.3000 7.8000
Y 15 5.1200 1.1245 0.2904 2.9000 7.7000
Diff (1-2)   -0.8762 1.3155 0.3672    

Confidence Limits

medschl Method Mean 95% CL Mean Std Dev 95% CL Std Dev
N   4.2438 3.9608 4.5268 1.3434 1.1709 1.5760
Y   5.1200 4.4973 5.7427 1.1245 0.8233 1.7735
Diff (1-2) Pooled -0.8762 -1.6045 -0.1479 1.3155 1.1571 1.5246
Diff (1-2) Satterthwaite -0.8762 -1.5480 -0.2043      

T-Tests

Method Variances DF t Value Pr > |t|
Pooled Equal 102 -2.39 0.0189
Satterthwaite Unequal 21.348 -2.71 0.0130

Equality of Variances

Equality of Variances
Method Num DF Den DF F Value Pr > F
Folded F 88 14 1.43 0.4640

Summary Panel

Summary Panel for infrisk

Q-Q Plots

Q-Q Plots for infrisk

Average patient age

Variable: age (Average patient age)

Statistics

medschl N Mean Std Dev Std Err Minimum Maximum
N 93 53.5129 4.6837 0.4857 38.8000 65.9000
Y 16 51.7688 3.2798 0.8199 44.2000 56.8000
Diff (1-2)   1.7442 4.5133 1.2215    

Confidence Limits

medschl Method Mean 95% CL Mean Std Dev 95% CL Std Dev
N   53.5129 52.5483 54.4775 4.6837 4.0938 5.4739
Y   51.7688 50.0211 53.5164 3.2798 2.4228 5.0761
Diff (1-2) Pooled 1.7442 -0.6774 4.1657 4.5133 3.9812 5.2110
Diff (1-2) Satterthwaite 1.7442 -0.2118 3.7001      

T-Tests

Method Variances DF t Value Pr > |t|
Pooled Equal 107 1.43 0.1563
Satterthwaite Unequal 26.834 1.83 0.0784

Equality of Variances

Equality of Variances
Method Num DF Den DF F Value Pr > F
Folded F 92 15 2.04 0.1200

Summary Panel

Summary Panel for age

Q-Q Plots

Q-Q Plots for age

Study of the Effectiveness of Nosocomial Infection Control

Elementary tests on the SENIC Data

One-way anova with proc glm

The GLM Procedure

The GLM Procedure

Data

Class Levels

Class Level Information
Class Levels Values
region 4 North Central Northeast South West

Number of Observations

Number of Observations Read 113
Number of Observations Used 108

Study of the Effectiveness of Nosocomial Infection Control

Elementary tests on the SENIC Data

One-way anova with proc glm

The GLM Procedure

Dependent Variable: infrisk Prob of acquiring infection in hospital

Analysis of Variance

infrisk

Overall ANOVA

Source DF Sum of Squares Mean Square F Value Pr > F
Model 3 15.7658812 5.2552937 3.09 0.0304
Error 104 177.0170818 1.7020873    
Corrected Total 107 192.7829630      

Fit Statistics

R-Square Coeff Var Root MSE infrisk Mean
0.081780 29.77625 1.304641 4.381481

Type I Model ANOVA

Source DF Type I SS Mean Square F Value Pr > F
region 3 15.76588117 5.25529372 3.09 0.0304

Type III Model ANOVA

Source DF Type III SS Mean Square F Value Pr > F
region 3 15.76588117 5.25529372 3.09 0.0304

Box Plot

Fit Plot for Prob of acquiring infection in hospital by Region of country (usa)

Study of the Effectiveness of Nosocomial Infection Control

Elementary tests on the SENIC Data

One-way anova with proc glm

The GLM Procedure

Means

region

infrisk

Distribution of infrisk by region

Distribution of infrisk by region

Means

Level of
region
N infrisk
Mean Std Dev
North Central 31 4.40967742 1.35014933
Northeast 27 4.93703704 1.25702584
South 34 3.91470588 1.45354996
West 16 4.38125000 0.87652248

Study of the Effectiveness of Nosocomial Infection Control

Elementary tests on the SENIC Data

One-way anova with proc glm

The GLM Procedure

Means

region

infrisk

Distribution of infrisk by region

Distribution of infrisk by region

Pairwise Multiple Comparisons

Tukey


Study of the Effectiveness of Nosocomial Infection Control

Elementary tests on the SENIC Data

One-way anova with proc glm

The GLM Procedure

Tukey's Studentized Range (HSD) Test for infrisk

Note:This test controls the Type I experimentwise error rate.

Information

Alpha 0.05
Error Degrees of Freedom 104
Error Mean Square 1.702087
Critical Value of Studentized Range 3.69260

Pairs

Comparisons significant at the 0.05 level are indicated by ***.
region
Comparison
Difference
Between
Means
Simultaneous 95% Confidence Limits  
Northeast - North Central 0.5274 -0.3694 1.4241  
Northeast - West 0.5558 -0.5189 1.6305  
Northeast - South 1.0223 0.1442 1.9004 ***
North Central - Northeast -0.5274 -1.4241 0.3694  
North Central - West 0.0284 -1.0202 1.0770  
North Central - South 0.4950 -0.3510 1.3409  
West - Northeast -0.5558 -1.6305 0.5189  
West - North Central -0.0284 -1.0770 1.0202  
West - South 0.4665 -0.5662 1.4993  
South - Northeast -1.0223 -1.9004 -0.1442 ***
South - North Central -0.4950 -1.3409 0.3510  
South - West -0.4665 -1.4993 0.5662  

Bonferroni


Study of the Effectiveness of Nosocomial Infection Control

Elementary tests on the SENIC Data

One-way anova with proc glm

The GLM Procedure

Bonferroni (Dunn) t Tests for infrisk

Note:This test controls the Type I experimentwise error rate, but it generally has a higher Type II error rate than Tukey's for all pairwise comparisons.

Information

Alpha 0.05
Error Degrees of Freedom 104
Error Mean Square 1.702087
Critical Value of t 2.68966

Pairs

Comparisons significant at the 0.05 level are indicated by ***.
region
Comparison
Difference
Between
Means
Simultaneous 95% Confidence Limits  
Northeast - North Central 0.5274 -0.3964 1.4511  
Northeast - West 0.5558 -0.5513 1.6629  
Northeast - South 1.0223 0.1178 1.9269 ***
North Central - Northeast -0.5274 -1.4511 0.3964  
North Central - West 0.0284 -1.0518 1.1086  
North Central - South 0.4950 -0.3764 1.3664  
West - Northeast -0.5558 -1.6629 0.5513  
West - North Central -0.0284 -1.1086 1.0518  
West - South 0.4665 -0.5973 1.5304  
South - Northeast -1.0223 -1.9269 -0.1178 ***
South - North Central -0.4950 -1.3664 0.3764  
South - West -0.4665 -1.5304 0.5973  

Scheffe


Study of the Effectiveness of Nosocomial Infection Control

Elementary tests on the SENIC Data

One-way anova with proc glm

The GLM Procedure

Scheffe's Test for infrisk

Note:This test controls the Type I experimentwise error rate, but it generally has a higher Type II error rate than Tukey's for all pairwise comparisons.

Information

Alpha 0.05
Error Degrees of Freedom 104
Error Mean Square 1.702087
Critical Value of F 2.69198

Pairs

Comparisons significant at the 0.05 level are indicated by ***.
region
Comparison
Difference
Between
Means
Simultaneous 95% Confidence Limits  
Northeast - North Central 0.5274 -0.4486 1.5033  
Northeast - West 0.5558 -0.6139 1.7255  
Northeast - South 1.0223 0.0666 1.9781 ***
North Central - Northeast -0.5274 -1.5033 0.4486  
North Central - West 0.0284 -1.1129 1.1697  
North Central - South 0.4950 -0.4257 1.4157  
West - Northeast -0.5558 -1.7255 0.6139  
West - North Central -0.0284 -1.1697 1.1129  
West - South 0.4665 -0.6575 1.5906  
South - Northeast -1.0223 -1.9781 -0.0666 ***
South - North Central -0.4950 -1.4157 0.4257  
South - West -0.4665 -1.5906 0.6575  

Study of the Effectiveness of Nosocomial Infection Control

Elementary tests on the SENIC Data

Scatterplot

The PLOT Procedure

Plot of infrisk*nurses

                                    Plot of infrisk*nurses.  Legend: A = 1 obs, B = 2 obs, etc.                                     
                                                                                                                                    
         |                                                                                                                          
         |                                                                                                                          
       8 +                                                                                                                          
     P   |              A                                                                                                           
     r   |                                              A           A                                                               
     o   |                                                                                                                          
     b   |                                                                                                                          
         |                                                                                                                          
     o 7 +                                                                                                                          
     f   |                                                                                                                          
         |                               A                                                                                          
     a   |                              A                                                                                           
     c   |             A    A           A                                                                                           
     q   |                             A                               A                                                            
     u 6 +                                                                                                                          
     i   |         A                                              A                                                                 
     r   |                          B               A A                    A                                                        
     i   |                A   A               A                              A                                                      
     n   |          A  A            A A                               A                                                             
     g   |              A    A             A      A                                                                                 
       5 +                          A       A                    AA                                                                 
     i   |                   AA      A A                                           A        A                        A              
     n   |         A      A  A   A                                                                               A                  
     f   |              AA       A  A   A      A      A                                                                             
     e   |           A     A  AA  A      AA B                 A                A                A                                   
     c   |        A A  A      A     A       A      A                                           A                                    
     t 4 +                                        A                                                                                 
     i   |                              A   A                      A              A                                                 
     o   |        A      A     A               A                                                                                    
     n   |           A         A                                                                                                    
         |            A         A                                                                                                   
     i   |      A         A                                                                                                         
     n 3 +           A                                                                                                              
         |        A   A                   AA                                                                                        
     h   |          AB                                                                                                              
     o   |              A                                                                                                           
     s   |                 A                                                                                                        
     p   |       A                                                                                                                  
     i 2 +           B                                                                                                              
     t   |        A                                                                                                                 
     a   |          A A                                                                                                             
     l   |                                                                                                                          
         |    AB                                                                                                                    
         |                                                                                                                          
       1 +                                                                                                                          
         |                                                                                                                          
         ---+---------------+---------------+---------------+---------------+---------------+---------------+---------------+--     
            0              100             200             300             400             500             600             700      
                                                                                                                                    
                                                    Aver # nurses during study period                                               
                                                                                                                                    
NOTE: 6 obs had missing values.                                                                                                     

Study of the Effectiveness of Nosocomial Infection Control

Elementary tests on the SENIC Data

Scatterplot

Plot of infrisk*nurses

                                        Plot of infrisk*nurses.  Symbol is value of medschl.                                        
                                                                                                                                    
         |                                                                                                                          
         |                                                                                                                          
       8 +                                                                                                                          
     P   |              N                                                                                                           
     r   |                                              N           Y                                                               
     o   |                                                                                                                          
     b   |                                                                                                                          
         |                                                                                                                          
     o 7 +                                                                                                                          
     f   |                                                                                                                          
         |                               N                                                                                          
     a   |                              N                                                                                           
     c   |             N    N                                                                                                       
     q   |                             N                               Y                                                            
     u 6 +                                                                                                                          
     i   |         N                                              Y                                                                 
     r   |                          N               N Y                    Y                                                        
     i   |                N   N               N                              N                                                      
     n   |          N  N            N N                               Y                                                             
     g   |              N                  N      N                                                                                 
       5 +                          N       Y                    NN                                                                 
     i   |                   NN      N N                                           Y        N                        Y              
     n   |         N      N  N   N                                                                               Y                  
     f   |              NN       N  Y   N      N      N                                                                             
     e   |           N        NN  N      NN N                 N                N                N                                   
     c   |        N N  N      N     N       N      N                                           N                                    
     t 4 +                                        Y                                                                                 
     i   |                              N   N                      N              Y                                                 
     o   |        N      N     N               N                                                                                    
     n   |           N         N                                                                                                    
         |            N         N                                                                                                   
     i   |      N         N                                                                                                         
     n 3 +           N                                                                                                              
         |        N   N                    Y                                                                                        
     h   |          NN                                                                                                              
     o   |              N                                                                                                           
     s   |                 N                                                                                                        
     p   |       N                                                                                                                  
     i 2 +           N                                                                                                              
     t   |        N                                                                                                                 
     a   |          N N                                                                                                             
     l   |                                                                                                                          
         |    NN                                                                                                                    
         |                                                                                                                          
       1 +                                                                                                                          
         |                                                                                                                          
         ---+---------------+---------------+---------------+---------------+---------------+---------------+---------------+--     
            0              100             200             300             400             500             600             700      
                                                                                                                                    
                                                    Aver # nurses during study period                                               
                                                                                                                                    
NOTE: 6 obs had missing values.  5 obs hidden.                                                                                      

Study of the Effectiveness of Nosocomial Infection Control

Elementary tests on the SENIC Data

Correlation Matrix

The CORR Procedure

The CORR Procedure

Variables Information

9 Variables: stay age infrisk culratio xratio nbeds census nurses service

Simple Statistics

Simple Statistics
Variable N Mean Std Dev Sum Minimum Maximum Label
stay 113 9.64832 1.91146 1090 6.70000 19.56000 Av length of hospital stay, in days
age 113 53.23186 4.46161 6015 38.80000 65.90000 Average patient age
infrisk 108 4.38148 1.34228 473.20000 1.30000 7.80000 Prob of acquiring infection in hospital
culratio 113 15.68407 10.18304 1772 1.60000 60.50000 # cultures / # no hosp acq infect
xratio 113 81.63009 19.36674 9224 39.60000 133.50000 # x-rays / # no signs of pneumonia
nbeds 113 252.17699 192.84516 28496 29.00000 835.00000 Average # beds during study period
census 109 191.36697 153.56086 20859 20.00000 791.00000 Aver # patients in hospital per day
nurses 112 170.60714 137.02018 19108 14.00000 656.00000 Aver # nurses during study period
service 113 43.15487 15.20019 4877 5.70000 80.00000 % of 35 potential facil. & services

Pearson Correlations

Pearson Correlation Coefficients
Prob > |r| under H0: Rho=0
Number of Observations
  stay age infrisk culratio xratio nbeds census nurses service
stay
Av length of hospital stay, in days
1.00000
 
113
0.18891
0.0451
113
0.54247
<.0001
108
0.33354
0.0003
113
0.38236
<.0001
113
0.40924
<.0001
113
0.46643
<.0001
109
0.32739
0.0004
112
0.35572
0.0001
113
age
Average patient age
0.18891
0.0451
113
1.00000
 
113
0.00327
0.9732
108
-0.23593
0.0119
113
-0.01893
0.8423
113
-0.05884
0.5359
113
-0.04964
0.6082
109
-0.08718
0.3607
112
-0.04064
0.6691
113
infrisk
Prob of acquiring infection in hospital
0.54247
<.0001
108
0.00327
0.9732
108
1.00000
 
108
0.57558
<.0001
108
0.45082
<.0001
108
0.32831
0.0005
108
0.34391
0.0003
106
0.35659
0.0002
107
0.39089
<.0001
108
culratio
# cultures / # no hosp acq infect
0.33354
0.0003
113
-0.23593
0.0119
113
0.57558
<.0001
108
1.00000
 
113
0.42707
<.0001
113
0.14879
0.1158
113
0.16192
0.0926
109
0.22481
0.0172
112
0.18239
0.0532
113
xratio
# x-rays / # no signs of pneumonia
0.38236
<.0001
113
-0.01893
0.8423
113
0.45082
<.0001
108
0.42707
<.0001
113
1.00000
 
113
0.04597
0.6288
113
0.02479
0.7981
109
0.04426
0.6431
112
0.11199
0.2376
113
nbeds
Average # beds during study period
0.40924
<.0001
113
-0.05884
0.5359
113
0.32831
0.0005
108
0.14879
0.1158
113
0.04597
0.6288
113
1.00000
 
113
0.98029
<.0001
109
0.91371
<.0001
112
0.79481
<.0001
113
census
Aver # patients in hospital per day
0.46643
<.0001
109
-0.04964
0.6082
109
0.34391
0.0003
106
0.16192
0.0926
109
0.02479
0.7981
109
0.98029
<.0001
109
1.00000
 
109
0.90468
<.0001
109
0.77258
<.0001
109
nurses
Aver # nurses during study period
0.32739
0.0004
112
-0.08718
0.3607
112
0.35659
0.0002
107
0.22481
0.0172
112
0.04426
0.6431
112
0.91371
<.0001
112
0.90468
<.0001
109
1.00000
 
112
0.78076
<.0001
112
service
% of 35 potential facil. & services
0.35572
0.0001
113
-0.04064
0.6691
113
0.39089
<.0001
108
0.18239
0.0532
113
0.11199
0.2376
113
0.79481
<.0001
113
0.77258
<.0001
109
0.78076
<.0001
112
1.00000
 
113

Study of the Effectiveness of Nosocomial Infection Control

Elementary tests on the SENIC Data

Simple regression with proc glm

The GLM Procedure

The GLM Procedure

Data

Number of Observations

Number of Observations Read 113
Number of Observations Used 107

Study of the Effectiveness of Nosocomial Infection Control

Elementary tests on the SENIC Data

Simple regression with proc glm

The GLM Procedure

Dependent Variable: infrisk Prob of acquiring infection in hospital

Analysis of Variance

infrisk

Overall ANOVA

Source DF Sum of Squares Mean Square F Value Pr > F
Model 1 24.2910097 24.2910097 15.30 0.0002
Error 105 166.7372146 1.5879735    
Corrected Total 106 191.0282243      

Fit Statistics

R-Square Coeff Var Root MSE infrisk Mean
0.127159 28.84189 1.260148 4.369159

Type I Model ANOVA

Source DF Type I SS Mean Square F Value Pr > F
nurses 1 24.29100969 24.29100969 15.30 0.0002

Type III Model ANOVA

Source DF Type III SS Mean Square F Value Pr > F
nurses 1 24.29100969 24.29100969 15.30 0.0002

Solution

Parameter Estimate Standard
Error
t Value Pr > |t|
Intercept 3.765525344 0.19662405 19.15 <.0001
nurses 0.003503216 0.00089571 3.91 0.0002

Fit Plot

Fit Plot for infrisk by Aver # nurses during study period
Procedure
Procedure