You run a landscaping company and need to know the average time it takes to plant a large tree for scheduling purposes. In the past it has taken 2.5 hours, but you wonder if that has changed. You collect data on planting time (in hours) in a random sample of 10 plantings and produce the following description of the data.
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Planting Time (hours)
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| |
|
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Mean
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2.4
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Mode
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2.8
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|
Standard Deviation
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0.516397779
|
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Sample Variance
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0.266666667
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Range
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1.6
|
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Minimum
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1.6
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Maximum
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3.2
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Count
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10
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a. What is the point estimate of the population mean planting time?
b. What is the 99% interval estimate for the population mean planting time?
c. Test the hypothesis that the population mean planting time has changed, i.e. that it is no longer 2.5 hours. Test at the 1% level of significance.
d. Did you have to make an assumption in order to work parts (b) and (c)? Explain.