Testing hypotheses by the Excel
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There are four auto body shops in a community and all claim to promptly serve customers. To check if there is any difference in service customers are randomly selected from each repair shop and their waiting times in days are recorded. The out put from a statistical software package is
Summary
Groups Count Sum Average Variance
Group A 3 15.4 5.133333 0.323333
Group B 4 32 8 1.433333
Group C 5 25.2 5.04 0.748
Group D 4 25.9 6.475 0.595833
ANOVA
Source of variation SS DF MS F P-value
Between groups 23.37321 3 7.791069 9.612506 0.001632
With in groups 9.726167 12 0.810514
Total 33.09938 15
Is there evidence to suggest a difference in the mean waiting times at the four body shops? Use the .05 significance level.
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The solution contains detailed explanation of testing hypotheses by using Excel.
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From the given ANOVA table I copy it here,
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Summary
Groups Count Sum Average Variance
Group A 3 15.4 5.133333 ...
Education
- BSc , Wuhan Univ. China
- MA, Shandong Univ.
Recent Feedback
- "Your solution, looks excellent. I recognize things from previous chapters. I have seen the standard deviation formula you used to get 5.154. I do understand the Central Limit Theorem needs the sample size (n) to be greater than 30, we have 100. I do understand the sample mean(s) of the population will follow a normal distribution, and that CLT states the sample mean of population is the population (mean), we have 143.74. But when and WHY do we use the standard deviation formula where you got 5.154. WHEN & Why use standard deviation of the sample mean. I don't understand, why don't we simply use the "100" I understand that standard deviation is the square root of variance. I do understand that the variance is the square of the differences of each sample data value minus the mean. But somehow, why not use 100, why use standard deviation of sample mean? Please help explain."
- "excellent work"
- "Thank you so much for all of your help!!! I will be posting another assignment. Please let me know (once posted), if the credits I'm offering is enough or you ! Thanks again!"
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