In: Statistics and Probability
A researcher wants to examine the production capability of three manufacturing plants that utilize different production methods of the same part in order to select a plant as a supplier for a company. The effectiveness of each plant will be measured in the number of parts it can produce in an hour. Representative hourly production amounts are recorded from each plant over a period of 12 hours and provided to the researcher.
The results of each of the three plants are as follows:
Plant A |
Plant B |
Plant C |
131 |
141 |
108 |
111 |
165 |
185 |
165 |
174 |
190 |
188 |
185 |
206 |
175 |
172 |
175 |
173 |
188 |
197 |
188 |
145 |
186 |
186 |
177 |
221 |
145 |
162 |
214 |
132 |
151 |
211 |
128 |
147 |
214 |
123 |
133 |
208 |
The hypothesis being tested is:
H0: µ1 = µ2 = µ3
Ha: Not all means are not equal
Mean | n | Std. Dev | |||
153.8 | 12 | 28.35 | Plant A | ||
161.7 | 12 | 18.09 | Plant B | ||
192.9 | 12 | 30.26 | Plant C | ||
169.4 | 36 | 30.61 | Total | ||
ANOVA table | |||||
Source | SS | df | MS | F | p-value |
Treatment | 10,293.06 | 2 | 5,146.528 | 7.55 | .0020 |
Error | 22,507.83 | 33 | 682.056 | ||
Total | 32,800.89 | 35 |
The p-value is 0.0020.
Since the p-value (0.0020) is less than the significance level (0.05), we can reject the null hypothesis.
Therefore, we can conclude that there is a significant difference between the groups.
The graph is:
The assumptions of ANOVA are violated.
Plant C would be recommended as a supplier because it has the highest hourly production amounts.
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