One-Way ANOVA
Objective:
Analysis of variance (ANOVA) is a
statistical technique used to compare the means of two or more groups of
observations or treatments. The continuous variable is the
dependent variable and the independent variable is the groups.
The null hypothesis is that there is no difference between the groups.
The alternative hypothesis is that there are differences between the
groups.
Code in SAS should look like the following:
data
Clover; input Strain $ Nitrogen @@;
datalines;
3DOK1
19.4 3DOK1 32.6 3DOK1 27.0 3DOK1 32.1 3DOK1 33.0 3DOK5 17.7 3DOK5 24.8 3DOK5
27.9 3DOK5 25.2 3DOK5 24.3 3DOK4 17.0 3DOK4 19.4 3DOK4 9.1 3DOK4 11.9 3DOK4
15.8 3DOK7 20.7 3DOK7 21.0 3DOK7 20.5 3DOK7 18.8 3DOK7 18.6 3DOK13 14.3 3DOK13
14.4 3DOK13 11.8 3DOK13 11.6 3DOK13 14.2 COMPOS 17.3 COMPOS 19.4 COMPOS 19.1
COMPOS 16.9 COMPOS 20.8;
Example code:
proc
glm data = Clover;
class
strain;
model
Nitrogen = Strain;
run;
Outputs:
The first table specifies the
number of levels and the values of the class variable.
The second table shows both the
number of observations read and the number of observations used. These values
are the same because there are no missing values in for any variable in the
model. If any row has missing data for a predictor or response variable, that
row is dropped from the analysis.
The third part is ANOVA analysis, which is the table here. The column
Pr>F indicates the p-value of anova analysis. If it is greater than
significant level, we reject null hypothesis. So there does not exist
differences between the groups. If it is less than significant level, we fail to reject
null hypothesis. So there exists differences
between the groups.