statistical methods for comparing of 2 1-year surveys

stat_analyst over 8 years ago

We would like to compare a percent from a 2013 single year dataset with the same percent from the 2014 single year data set. Can we use statistical methods that require independent samples like a chi - square test? Although different people may have been surveyed in the two years, I don't believe one year is independent of the next year because the samples represent the same population.

Thank you in advance for your help or thoughts.

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Gene Shackman over 8 years ago

Couple of comments:
1. having the samples from the same population doesn't necessarily mean the samples are not independent. The sample size is small compared to the population, so they could be entirely different people.

2.The design and method of the ACS is here www.census.gov/.../design-and-methodology.html One page of doc (chapter 4, page 4) says "One of the ACS design requirements is that no HU address be in sample more than once in any five-year period." So looks like 2013 and 2014 are independent samples.
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Gene Shackman over 8 years ago

Couple of comments:
1. having the samples from the same population doesn't necessarily mean the samples are not independent. The sample size is small compared to the population, so they could be entirely different people.

2.The design and method of the ACS is here www.census.gov/.../design-and-methodology.html One page of doc (chapter 4, page 4) says "One of the ACS design requirements is that no HU address be in sample more than once in any five-year period." So looks like 2013 and 2014 are independent samples.
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stat_analyst over 8 years ago in reply to Gene Shackman

Yes, that's what is confusing. The samples are independent but the populations are not. Usually when we talk about independent samples both are independent like men vs. women.
Anyway, I found the formulas that ACS recommends. So, I will use those instead of chi-square www.census.gov/.../acs_accuracy_of_data_2010.pdf. Thank you for commenting.
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stat_analyst over 8 years ago in reply to stat_analyst

The formula that ACS gives is a paired samples samples Z-test, so I'm going to take that as evidence that my hunch that these are dependent samples is true.
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Gene Shackman over 8 years ago in reply to stat_analyst

Could you point to the formula you mean? What page?
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stat_analyst over 8 years ago in reply to Gene Shackman

The formula is on page 23.
After you weight them both years represent the entire US population which doesn't change much from one year to the next. So, the values from one year are very much related to the values from the other year. So, I think the samples are independent but the populations are dependent. Most people say independent samples but they could just as easily say independent populations, I think both need to be true for independence.
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