The Gallup organization published the results of a recent poll on caregivers.

The poll used a sample of people who are caring for another person in their family.  It reported that most of them (7 out of 10) are taking care of a parent or another elderly person.  The report indicated that caregivers spend on average 13 days per month running errands for the person and 6 days per month helping the person eat, dress, bathe, or do other personal care. 

Questions about the story:

1.  How did Gallup find and sample these caregivers?  Do their methods mean that the results are generalizable to most American caregivers?  

2.  How might you assess the construct validity of this poll?  

3.  How confident are you in concluding that about 36% of people who are caregivers in the United States are living with the person they are caring for?  

4. What's the margin of error on the 36% value?  (The one that refers to the proportion of people who are living with the person they are caring for).  How do you know?  

After reading the polling methods, can you say with confidence that most caregivers, like this New York woman, are caring for aging parents?

Photo: Nicole Bengiveno/The New York Times/Redux

 

Suggested answers

1.  The Survey Methods section indicates that Gallup re-contacted people they had polled the year before and who happened to have self-identified as "caregivers."  Since almost all of Gallup's polls are conducted on probability samples, this means that the caregivers themselves were presumably selected from a random sample of Americans originally.  They were then recontacted to participate in the present poll.  This means that the sample used is probably very close to a probability sample of American caregivers.  (Of course, some of the caregivers may not have been willing to participate the second time, or may not have been reached the second time, which could bias the sample in some way.)  All in all, this sample seems reasonably generalizable. 

2.  It is difficult to assess the construct validity of this poll because they do not include the question wording they used.  Therefore, it's hard to evaluate how well they measured their variables.

3.  In my opinion, this is probably a good estimate.  First, the sample seems fairly representative (see #1, above).  Second, it seems that the construct of living with the person they are caring for is a rather simple, behavioral question to measure.  Its construct validity is likely to be good.  (But of course, it would be best to see the actual question used.)

4.  Looking in the Survey Methods section, you can read, "For results based on the total sample of national adults, one can say with 95% confidence that the maximum margin of sampling error is ±2 percentage points. For smaller groups, such as full-time employed caregivers, the maximum margin of sampling error is ±2.3 percentage points."  

This means that the standard error of the estimate is 2%.  So if you conducted the same poll using the same methods 100 times, 95 of the times the value (are you living with the person you are caring for?) will be between 34 and 38%.  

Incidentally, you can see that the standard error of the smaller groups (such as full time employed caregivers) is larger.  That's because there are fewer people in this sample.  The smaller the sample, the larger the standard error of the estimate. (See Table 6.1 in the text.)