## 6. Discuss the procedure of ANOVA.

In analysis of variance, a continuous response variable, known as a dependent variable, is measured under experimental conditions identified by classification variables, known as independent variables.The variation in the response is assumed to be due to effects in the classification, with random error accounting for the remaining variation.

The steps below explain the procedure of Anova. The general logic of analysis of variance is the same as that of significance tests. That is, you assume H0 to be true and then determine whether the obtained sample result is rare enough to raise doubts about H0.

To do this, convert the sample result into a test statistic (F, in this case). Then locate it in the theoretical sampling distribution (the F distribution). If the test statistic falls in the region of rejection, H0 is rejected; if not, H0 is retained. The only new twist is that if H0 is rejected, follow-up testing is required to identify the
specific source(s) of significance.

### Step 1 Formulate the statistical hypotheses and select a level of significance.

Ex: Let’s assume the statistical hypotheses to be:
Ho → µ1 = µ2 = µ3
Let α=.05 be the level of significance.

### Step 4 Identify the region of rejection.

Let's say dfbetween = 2 and dfwithin = 6. The critical value of F is 5.14 (using tables). This is the value of F beyond which the most extreme 5% of sample outcomes will fall when H0 is true.

### Step 5 Make the statistical decision and form conclusions.

Because the sample F ratio falls in the rejection region (i.e., 7.75 > 5.14), we reject the Null Hypothesis.

The overall F ratio is statistically significant (α = .05), so we conclude that the population means differ in some way.
Next, conduct post hoc comparisons to determine the specific source(s) of the statistical significance.

### Step 6 Conduct Tukey’s HSD test.

• Calculate HSD and Compare HSD with each difference between sample means
• Make the statistical decisions and form conclusions:
Group 1 is significantly different from Groups 2 and 3; the difference between Groups 2 and 3 is not significant
* * *

Above is the procedure of Analysis of Variance.

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