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# Conclude the Mean

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The manager of a department store wishes to study the number of minutes top salespeople at his store spend at their computer terminals in order to process "end of day closing" by the department name.

The manager selected a sample of 5 (five) salespeople from each of three departments.

At the .05 significance level, can she conclude there is a difference in the mean number of minutes spent at doing the "end of day closing" per week by department?

(see data in the attached file)

##### Solution Summary

The manager of a department store wishes to study the number of minutes top salespeople at his store spend at their computer terminals in order to process "end of day closing" by the department name.

The manager selected a sample of 5 (five) salespeople from each of three departments.

At the .05 significance level, can she conclude there is a difference in the mean number of minutes spent at doing the "end of day closing" per week by department?

##### Solution Preview

Electronics Toys Clothing
30 10 15
25 15 10
27 16 12
31 14 11
24 13 18

The manager of a department store wishes to study the number of minutes top salespeople at his store spend at their computer terminals in order to process "end of day closing" by the department name.

The manager selected a sample of 5 (five) salespeople from each of three ...

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###### 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!"
• "Thank you"
• "Thank you very much for your valuable time and assistance!"

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