To determine if there are significant differences between the means of the four samples, we will perform a One-Way Analysis of Variance (ANOVA) at a 5% level of significance.
Step 1: State the Hypotheses
- Null Hypothesis (H0): There is no significant difference between the means of the four samples.
H0:μA=μB=μC=μD
- Alternative Hypothesis (H1): At least one sample mean is significantly different from the others.
H1:Atleastoneμj is different
The significance level is α=0.05.
Step 2: Calculate Descriptive Statistics for Each Sample
Let nj be the number of observations in sample j, ∑xj be the sum of observations, and ∑xj2 be the sum of squared observations.
- Sample A: nA=5
∑xA=9+7+12+14+13=55
xˉA=11
∑xA2=92+72+122+142+132=81+49+144+196+169=639
- Sample B: nB=6
∑xB=18+12+15+13+16+16=90
xˉB=15
∑xB2=182+122+152+132+162+162=324+144+225+169+256+256=1374
- Sample C: nC=6
∑xC=10+9+11+10+7+10=57
xˉC=9.5
∑xC2=102+92+112+102+72+102=100+81+121+100+49+100=551
- Sample D: nD=6
∑xD=13+8+9+12+11+10=63
xˉD=10.5
∑xD2=132+82+92+122+112+102=169+64+81+144+121+100=679
Step 3: Calculate Overall Statistics
Total number of observations N=nA+nB+nC+nD=5+6+6+6=23.
Grand Sum ∑X=55+90+57+63=265.
Grand Sum of Squares ∑X2=639+1374+551+679=3243.
Correction Factor CF=N(∑X)2=232652=2370225≈3053.2609.
Step 4: Calculate Sum of Squares
- Sum of Squares Total (SST):
SST=∑X2−CF=3243−3053.2609=189.7391
- Sum of Squares Between Treatments (SSTreatment):
SSTreatment=∑j=1knj(∑xj)2−CF
SSTreatment=(5552+6902+6572+6632)−3053.2609
SSTreatment=(53025+68100+63249+63969)−3053.2609
SSTreatment=(605+1350+541.5+661.5)−3053.2609
SSTreatment=3158−3053.2609=104.7391
- Sum of Squares Within Treatments (SSError):
SSError=SST−SSTreatment=189.7391−104.7391=85.0000
Step 5: Calculate Degrees of Freedom (df)
- df for Treatments (df1=k−1): 4−1=3
- df for Error (df2=N−k): 23−4=19
- df Total (N−1): 23−1=22
Step 6: Calculate Mean Squares (MS)
- Mean Square for Treatments (MSTreatment):
MSTreatment=df1SSTreatment=3104.7391≈34.9130
- Mean Square for Error (MSError):
MSError=df2SSError=1985.0000≈4.4737
Step 7: Calculate the F-statistic
F=MSErrorMSTreatment=4.473734.9130≈7.8041
Step 8: Determine the Critical F-value
For α=0.05, df1=3, and df2=19, the critical F-value from the F-distribution table is approximately Fcritical=3.127.
Step 9: Make a Decision
Since the calculated F-statistic (7.8041) is greater than the critical F-value (3.127), we reject the null hypothesis (H0).
Step 10: State the Conclusion
There is sufficient evidence to conclude that there are significant differences between the means of the treatments (samples A, B, C, D) at the 5% level of significance.
The final answer is Yes,therearesignificantdifferencesbetweenthemeansofthetreatments.
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