The average height of Hackberry trees in Virginia was investigated by placing 10

Question

The average height of Hackberry trees in Virginia was investigated by placing 100 ten-hectare plots randomly on a distribution map of the species in Virginia using a computer. Researchers then found the location of each random plot in the field, and then they measured the height of every Hackberry tree within each of the 10-hectare plots. The average height within the plot was used as the unit measurement. These unit measurements were then used to estimate the average height of Virginia Hackberry trees.

Is the estimate of height based on 100 plots influenced by sampling error?  (yes or no)

If a new estimate based on another random sample of 100 was taken, is it likely it would be the exact same estimate of age?  (yes or no)

How would the sampling error of the estimate of mean age change if the investigators had used a sample of 500 plots?  (increase, decrease, stay the same)

Were the trees randomly sampled?  (yes or no)

Were the 10-ha plots randomly sampled?  (yes or no)

The researchers took an average of the height of trees within each plot as their unit measurement. Would combining the heights of all of the Hackberry trees from all of the plots be an alternate and equivalent unit measurement?  (yes or no)

What was the reason that the researchers took an average of the height of trees within each plot as their unit measurement, rather than combining into a single sample the height of all the trees from all the plots?

What is the population of interest in this study?

Explanation / Answer

Solution

(a) Yes, Since the sample does not include all members of the population.

(b) No, it will be different

(c) Decrease, as sample size is being increased from 100 to 500.(inverse relationship between sampling error and the sample size)

(d) Yes, trees were randomly sampled from computer

(e) Yes

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