Question

In: Statistics and Probability

Examine the three samples obtained independently from three populations: Population Data 3 Item Group 1 Group...

Examine the three samples obtained independently from three populations:

Population Data 3

Item Group 1 Group 2 Group 3
1 14 17 17
2 13 16 14
3 12 16 15
4 15 18 16
5 16 14
6 16
  1. Conduct a one-way analysis of variance on the data assuming the populations have equal variances and the populations are normally distributed. Use alpha = 0.05.
  2. If warranted, use the Tukey-Kramer procedure to determine which populations have different means. Use an alpha level of 0.05.

Solutions

Expert Solution

A single factor ANOVA is used in excel to test the null hypothesis that all the means are equal. The hypothesis is defined as,

Null Hypothesis: At least one mean differ significantly.

Alternative Hypothesis: All the means are equal,  

The test is performed in excel by using following steps,

Step 1: Write the data values in excel. The screenshot is shown below,

Step 2: DATA > Data Analysis > ANOVA: single Factor > OK.  The screenshot is shown below,

Step 3: Select Input Range: All the data values column, Alpha = 0.05. The screenshot is shown below,

The result is obtained.  The ANOVA table is shown below,

From the ANOVA result summary,

Since the P-value is less than 0.05 at 5% significance level, the null hypothesis is rejected. Hence we can conclude that there is atleast one mean is significantly differ.

Post-Hoc test

Now, the Tukey-Kramer (T-K) multiple comparisons procedure is used to test all the pairwise comparison and identify which pair is significantly different.

The Tukey-Kramer method uses the formula,

The q value is obtained using the Studentized Range q table for significance level = 0.05, number of groups, k = 3, degree of freedom = N - k = 15 - 3 = 12.

The HSD value for group 1 and 2 comparison ,

The HSD value for group 1 and 3 comparison ,

The HSD value for group 2 and 3 comparison ,

Now,

The mean value for each groups are,

Groups Average
Group 1 14
Group 2 16.75
Group 3 15.33333

There are 3 possible comparison as follows,

Comparison Difference HSD
2.75 > 2.3153 Significant
1.333333 < 2.0899 Not Significant
1.416667 < 2.2279 Not Significant

The mean difference in Group 1 vs Group 2 is significant.


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