Question 1
Throughout the length of this study, the researchers introduced new participants to adjust for a population increase, altered participant selection methods from choosing one household member to all eligible household members, changed the method of dietary data collection from written to electronic, and modified age eligibility requirements from 74 to 84 years of age. Do you feel that these factors impacted the results of the study? What are the drawbacks of conducting a study that takes place over several decades?
posted by Brooke S @ 2:50 PM
16 comments
16 Comments:
Initially I thought yes, but after thinking more about this question and the purpose of this study I don't think changing these factors would have a huge impact. By adding new participants, including all eligible participants and increasing the age requirements they were simply increasing their sample size. Changing the data collection from written to electronic may have had a larger impact. Not only could data be impacted during that time of the switch but one method may be more effective than the other. Conducting a study over several decades would be challenging for many reasons but one of the major ones that impacted this study is technology changing and evolving you would have to make changes with the times.
I do think some of these things would alter the results of the study. Adding new participants to account for population increase is not something I think would affect results, but changing from written to electronic forms, and modifying age requirements are things that I think would affect results. If you are allowing a older age group to join in later, you have missed out on collecting data from that age group in previous years. Also, some people are not able to understand and thoroughly use electronic forms.
I do think these factors impacted the results of the study. I think adding members to account for the population increase was good but the change from pencil to electronic data collection and the modified age of eligibility could have had a major effect on the results. Many of the participants may not have understood how to use the new technology so they may have failed to do the survey. I think keeping age eligibility should be kept consistent throughout an entire study no matter how long it lasts. Including the older population for some of the study may sway the results one way or the other. The drawbacks of conducting a study over a long period of time are clear in this study. Technology is constantly changing but I think it's important to keep the data collection as consistent as possible throughout the entire study.
Michela- I agree that adding the older group later on means you have missed collecting data from them earlier in the study. The results may have been completely different if this population was included in the beginning. I think it throws the study off if a new variable is added in the middle of it.
I think that all these changes would create an issue. The initial goal of the study may be lost in trying to keep it alive. Also, the long duration is useful in providing comprehensive information, but as is seen in this study many alterations may need to be made to keep the study current.
I do not feel that increasing the sample size would have a negative impact on the results. If anything, it would be more accurate to report the data on a larger sample group. However, I feel that increasing the age of the participants may impact the results. As one ages, dietary intake can decrease in many indiviudals which would directly impact Vit D intake.
I agree with Michela that comprehension of the new forms may have played a factor in the results. But like Jamie said, since this was an on-going study, the most up-to-date data collection materials should be used.
I agree with stephanie that increasing the sample size would not affect the results, but agree with the others who said increasing the age requirements would have an effect. I'm not sure what I think about the change to computerized surveying. The paper did note that there was a comparability that showed that results from the in-person and computerized methods were not significantly different.
The fact that this study was altered in multiple ways does make me question the validity of the data. With every change to the original format, I feel that a new study began. I look at this article as multiple studies’ results pooled together and not one long term study. I do not feel that the drawbacks in this study were from the length of time but from some of the decisions made by the researchers to alter the study in the ways that they did.
It sounds like everyone for one reason or another believe that this study lost some valid thru the mist of all the different changes. It is shocking how many variables were altered along the way
I do not think that increasing participants to correct for increased population size would alter any results. If the numbers are generally kept consistent I think it would help provide more consistent results. I do not know how letting all household members would alter or change overall results. It is very likely the entire family would follow the same dietary pattern. So if all members participate then you would just have more results. As for the change of data collection from written to electronic, there could be errors that could change some results. However, I feel like there will probably be just as many errors on the written version that the electronic. I also do not think changing the age from 74 to 84 would really alter or affect and results.
Kevin-
It does kind of seem like this study tried to compile too much within it. However, I feel it was a great idea to do a long term study on vitamin d intake.
I think that increasing population size would alter the results of the study but that is what the researchers wanted when they were trying to correct for the population increase. I also think that changing the other variables would impact results. From this, I can see that one of the drawbacks of a long term study is that researchers may need to continue reinventing the study to keep it relevant.
Kevin, it also makes me wonder how valid the end result is. I feel like every time you change a variable you change the study. Maybe it isn't as black and white as that but I do have the memory of a professor once saying that you should not change the variables after a study has begun.
I do think that this could impact the results. The switch in data collection could have been difficult for the older generation. They also modified age requirements could also have impacted the results. Changing the ages of the participants can greatly effect results because every generation is different.
Hmmm - I know where you all are coming from in saying that changing variables affects the results. Perhaps this is the best data set the researchers could find without making their own study and waiting 20 years. It does seem though like since the study surveyed different people each time, it doesn't really matter if they start including people from more neighborhoods part-way through the study.
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