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Observational study and some terms on design of experiment

Nonsmokers
4194 3522
3454
3062 3771 3783
3544 3746 4019
4248 3719 3668
3128 3290 3423
3471 4354 3544
3994 2976 4067
3732 3823 3302
3436 3976 3263
Smokers
3998 3455 3066
3150 2986 2918
4216 3502 3457
2860 3282 2746
3686 2851 3145
3807 3548 4104
3963 3892 2768
3769 3509 3629
4131 3129 4263
Is this an observational study or a designed experiment? Why?
What is the explanatory variable? What is the response variable?
Can you think of any lurking variables that may affect the results of the study?
Go to http://www.xuru.org/st/DS.asp and find the summary statistics for both non-smokers and smokers (mean, median, standard deviation, quartiles.) Compute each group separately. Report your findings. Note: Copy the data from the tables and place in the large box on the page and separate each item by a comma.
Why is the sample standard different from the population standard deviation? Which should you use in this study, and why?
Using your results, write up a practical summary of what you are seeing in this data. Do you agree with the researchers' conclusions based on your analysis?

Solution Preview

Is this an observational study or a designed experiment? Why?
This is an observational study because no treatment is applied to experimental units (ie. Both smokers and non-smokers).

What is the explanatory variable? What is the response variable?
The independent variable is the personal smoking habit. There are two level: smoking or non-smoking. The depedent variable is weight of baby.

Can you think of any lurking variables that may affect the results of the study?
Because only women can birth baby, I may consider mother's health condition as a lurking variable.

Go to http://www.xuru.org/st/DS.asp and find the summary statistics ...

Solution Summary

The solution gives detailed discussion on observational study and some terms on design of experiment including dependent variable, mean, median, standard deviation and so on.

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