Question

Perform's Tukey's multiple comparison procedure in SAS (using alpha = 0.05) and summarize 
which insecticides are significantly different from each other, in terms of mean 
number of deaths.

data insectdeaths; 
input INSECTICIDE $  DEAD;
cards;
 A 85
 B 90
 C 93
 D 98
 A 82
 B 92
 C 94
 D 98
 A 83
 B 90
 C 96
 D 100
 A 88
 B 91
 C 95
 D 97
 A 89
 B 93
 C 96
 D 97
 A 92
 B 81
 C 94
 D 99
;
run;

Answer 1

Treat insecticides as a grouping variable using class statement in proc glm

use model statement  

Ho:

he mean number of insect deaths are same across insectside 
types. 

Ha:

The mean number of insect deaths differs across insectside 
types. 

SAS Code:

data insectdeaths;
input INSECTICIDE $ DEAD;
cards;
A 85
B 90
C 93
D 98
A 82
B 92
C 94
D 98
A 83
B 90
C 96
D 100
A 88
B 91
C 95
D 97
A 89
B 93
C 96
D 97
A 92
B 81
C 94
D 99
;
run;
proc glm data = insectdeaths;
class INSECTICIDE ;
model DEAD = INSECTICIDE ;
means INSECTICIDE/cldiff tukey ;
run;

Output:

The GLM Procedure

Class Level Information
Class	Levels	Values
INSECTICIDE	4	A B C D

Number of Observations Read	24
Number of Observations Used	24

The GLM Procedure

Dependent Variable: DEAD

Source	DF	Sum of Squares	Mean Square	F Value	Pr > F
Model	3	488.7916667	162.9305556	17.99	<.0001
Error	20	181.1666667	9.0583333
Corrected Total	23	669.9583333

R-Square	Coeff Var	Root MSE	DEAD Mean
0.729585	3.264029	3.009707	92.20833

Source	DF	Type I SS	Mean Square	F Value	Pr > F
INSECTICIDE	3	488.7916667	162.9305556	17.99	<.0001

Source	DF	Type III SS	Mean Square	F Value	Pr > F
INSECTICIDE	3	488.7916667	162.9305556	17.99	<.0001

The GLM Procedure

The GLM Procedure

Tukey's Studentized Range (HSD) Test for DEAD

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

Alpha	0.05
Error Degrees of Freedom	20
Error Mean Square	9.058333
Critical Value of Studentized Range	3.95825
Minimum Significant Difference	4.8635

Comparisons significant at the 0.05 level are indicated by ***.
INSECTICIDE Comparison	Difference Between Means	Simultaneous 95% Confidence Limits
D - C	3.500	-1.364	8.364
D - B	8.667	3.803	13.530	***
D - A	11.667	6.803	16.530	***
C - D	-3.500	-8.364	1.364
C - B	5.167	0.303	10.030	***
C - A	8.167	3.303	13.030	***
B - D	-8.667	-13.530	-3.803	***
B - C	-5.167	-10.030	-0.303	***
B - A	3.000	-1.864	7.864
A - D	-11.667	-16.530	-6.803	***
A - C	-8.167	-13.030	-3.303	***
A - B	-3.000	-7.864	1.864

since F=17.99,p<.0001,

p<0.05

Reject Ho that all the 4 type insecticides means are equal

and conclude that there is sufficient evidence at 5% level of significance that

he mean number of insect deaths differs across insectide 
types. 

From tukey,the following means are different

D-B

D-A

C-B

C-A

B-D

B-C

A-D

A-C