lesson 4: more 1-way anova. why can’t we do 3 individual 2 population tests? a. b. c. if each test...
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Lesson 4:
More 1-way ANOVA
Why can’t we do 3 individual 2 population tests?
• A.
• B.
• C.• If each test has a 5% significance level (the
single comparison-wise type one error) then the overall (experiment-wise type one error) significance level, denoted by alpha sub EW would be
Experimental Design
• Experimental Study
• Observational Study
• Completely Randomized Design
Example 1
• Four different paints are advertised as having the same drying time. To check the manufacturers’ claim, 5 random samples were tested for each of the paints. The time in minutes until the paint was dry enough for a second coat to be applied were recorded. The following table summarizes the results.
Paint 1 Paint 2 Paint 3 Paint 4
Mean 133 139 136 144
Std. Dev 6.89 7.07 4.58 7.38
n 5 5 5 5
Use a 5% significance level to see whether the mean drying time is the
same for each.• SSTR
• MSTR
• SSE
• MSE
ANOVA Table
Source DF SS MS F p
Factor
Error
Total
Example 2: Fabric Flammability Tests
• Flammability tests were conducted on children’s sleep wear. The Vertical Semi-restrained Test was used, in which pieces of fabric were burned under controlled conditions. After burning stopped, the length of the charred portion was measured and recorded. Random samples using the same material were obtained from each of 5 testing labs. Because the same fabric was used, the different labs should have obtained the same results. Is there sufficient evidence to support the claim that the mean lengths for the different labs are the same?
Lab 1 Lab 2 Lab 3 Lab 4 Lab 5
2.9 2.7 3.3 3.3 4.1
3.1 2.9 3.3 3.2 4.1
3.7 3.2 3.5 2.7 4.2
3.1 3.7 2.8 2.7 3.1
4.2 3.2 2.8 3.3 3.5
3.1 3.4 3.5 2.7 4.2
ANOVA Table
Source DF SS MS F p
Factor
Error
Total
Calculate Fisher LSD and determine where the differences liePopulations Mean Dif LSD Dif Y/N??
Lab 1 & 2
Lab 1 & 3
Lab 1 & 4
Lab 1 & 5
Lab 2 & 3
Lab 2 & 4
Lab 2 & 5
Lab 3 & 4
Lab 3 & 5
Lab 4 & 5