The One-Way Analysis of Variance (ANOVA) is like an extension of the two-sample t-test. It is use to compare the equality of more than two means. The residuals and fitted values of the response are shown in Columns AA:AB.
| Null Hypothesis, H0 | Alternate Hypothesis, H1 |
| m1 = m2 = ... = mi | m1 <> m2 <> ... <> mi |
where mi are the means of population i
At the Excel Menu (For Excel 2007, go to Add-ins first)
Choose ProcessMA > Statistics > ANOVA > One-Way ANOVA
For data in single stacked column
In Variable, select the column containing the response data (Numeric)
In Factor, select the column containing factor levels (>=2 levels)
For data in different columns
In Variables, select the columns containing the response data (Numeric, >= 2 variables)
In Confidence Level, enter the desired confidence level for the confidence interval (Numeric, >0 & <1)
Check Show Boxplot, if you want to display boxplot of the data
Check Plot Residual, if you want to display residual plots
Click OK
A company makes steel bolts using four different machines. You want to assess if the dimensions of the steel bolts made are the same for the different machines. You randomly selected 50 steel bolts made by each machine.
Open data worksheet by choosing ProcessMA > Tools > Data
Choose ProcessMA > Statistics > ANOVA > One-Way ANOVA
In Variable, select B - Dimension
In Factor, select C - Machine
Check Show Boxplot
Click OK
For a desired a = 0.05, since p = 0.3068> a, we fail to reject H0. Therefore, we conclude that there is no significant evidence that the dimensions of the steel bolts made by the different machines are different. It can also be observed from the individual confidence intervals that there are significant overlaps. The residual plots should also be examined to ensure that the residuals are normally distributed, centered about zero and random.
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