MATH 225N Week 6 Discussion: Confidence Interval
Initial Post Instructions
Thinking of the many variables tracked by hospitals and doctors’ offices,
... [Show More] confidence intervals could … created for population parameters (such as means or proportions) that were calculated from many of them.
Choose a topic of study that is tracked (or you would like to see tracked) from your place of work. Discuss the variable and parameter (mean or proportion) you chose, and explain why you would these to create an interval that captures the true value of the parameter of patients with 95% confidence.
Consider the following:
How would changing the confidence interval to 90% or 99% affect the study? Which of these values (90%, 95%, or 99%) would best suit confidence level according to type of study chosen? How might the study findings … presented to those in charge in an attempt to affect change at the workplace?
NB: 2 Answers Displayed
Confidence Intervals
In everyday terms, a confidence interval is the range of values around a sample statistic (such as mean or proportion) within which clinicians can expect to get the same results if they repeat the study protocol or intervention, including measuring the same outcomes the same ways. As you ask yourself, "Will I get the same results if I use this research?", you must address the precision of study findings, which is determined by the Confidence Interval. If the CI around the sample statistic is narrow, you can be confident you will get close to the same results if you implement the same research in your practice.
Consider the following example. Suppose that you did a systematic review of studies on the effect of tai chi exercise on sleep quality, and you found that tai chi affected sleep quality in older people. If, according to your study, you found the lower boundary of the CI to be .49, the study statistic to be 0.87, and the upper boundary to be 1.25, this would mean that each end limit is 0.38 from the sample statistic, which is a relatively narrow CI.
(UB + LB)/2 = Statistic [(1.25 + .49)/2 = .87]
Keep in mind that a mean difference of 0 indicates there is no difference; this CI does not contain 0. Therefore, the sample statistic is statistically significant and unlikely to occur by chance.
Because this was a systematic review, and tai chi exercise has been established from the studies you assessed as helping people sleep, based on the sample statistics and the CI, clinicians could now use your study and confidently include tai chi exercises among possible recommendations for patients who have difficulty sleeping.
Now you can apply your knowledge of CIs to create your own studies and make wise decisions about whether to base your patient care on a particular research finding.
Answer 1
Since I have become a nurse I have personally felt the intense low back pain that once use to be just a one-sided conversation. Low back pain (LBP) is a significant health concern worldwide. Although pharmacological therapies have been shown to be successful in reducing pain, each one carries a risk. My study consist of non-pharm approach to reducing pain. Because of time and cost I escheated the effects of pain and nonpharmacological intervention, such as music, breathing, acupuncture and massage to name a few. I work in surgery and we play music for patients. In the article Medical statistics: Hypothesis tests and Estimation, discussed the relative effectiveness of acupuncture and massage as treatments for chronic low back pain in patients presenting to primary care. The study showed the disparity in pain ratings between the two groups.
As we have been learning these pass weeks, it is not possible to be 100% sure of the range within which the population estimate will fall, so a degree of trust is added to the set of values. The 95% confidence interval for the mean difference in pain scores of 8.1 is (1.2,15.0). 90% confidence interval (2.3,13.9) which is narrower. 99% confidence interval (-1.0,17.2) is wider than the 95% CI. Not having a value 0 between two of the ranges will not have a significant difference in mean pain scores. Thus, by widening the range of values this increase the uncertainty and the interval now includes 0 therefore it is possible, this confidence level, now has no difference in mean pain score between the two groups.
As we learned in Week 6 lesson, it states confidence intervals in medicine include a range within which test results or measurements may be predicted (chamberlain, 2020). Although pharmacological therapies have been shown to be successful in reducing pain, each one carries a risk of potentially severe side effects, this study was able to show that nonpharmacological intervention has been effective.
Work Cited
Holmes, A., Illowsky, B., & Dean, S. (2017). Introductory business statistics. OpenStax. https://openstax.org/details/books/introductory-business-statistics
Thomas, E., An introduction to medical statistics for health care professional: Hypothesis tests and estimation (2005). Retrieved from https://onlinelibrary.wiley.com/doi/pdf/10.1002/msc.30
Answer 2
I work on med-surg/ortho floor. Preventing HAC (Hospital Acquired Conditions) is a big thing in hospitals because HAC’s lead to non-payment to the hospital which leads to the hospital having to pay for these conditions and they are pricey! In order for the hospital to operate/function, costs need to be cut/optimized, and what better way to cut costs than to prevent them as much as possible?! For this discussion, instead of all HAC’s, I will focus on SSI (Surgical Site Infections) which one of the many HAC’s, but specific to my area of work. The hospital does many things to bring these infection rates down to the minimum including preop labs, preop/postop antibiotics, preop CHG bathing, and other prevention methods. Even with prevention, surgical site infections still occur.
For examples sake, let’s say in 3 months’ time, there are 400 total joint arthroplasties performed at my hospital. Of these 400 patients, 5 patients acquired a surgical site infection (HAC). This would give me a sample proportion of 0.0125 meaning that 1.25% of total joint arthroplasty patients acquired an HAC/SSI. Using week 6 excel spreadsheet, “we can then expect that the population value will be within that interval”, and I can be 95% confident that population proportion of SSI’s after total knee arthroplasty surgery would fall between 0.16% and 2.34% (Chamberlain College of Nursing, 2019).
Increasing the sample size would decrease the interval, therefore making the distance between the lower limit and upper limit smaller, which would increase the accuracy of the study. When I use the excel spreadsheet to increase my confidence level to 99%, it gives me a negative lower limit, which means my sample size is too small to get a 99% confidence interval. When I increase the sample size to 800 and the number of infections/successes to 10 (same proportion), it gives me an interval of .24% to 2.26%. When I use my original sample proportion with a 90% confidence level, it gives me an interval of .34% to 2.16%. “The selection of a confidence level for an interval determines the probability that the confidence interval produced will contain the true parameter value” (Mackowiak, Wasserman, & Levine, 1992). With my particular study, and the sample size being 400 patients, 95% is the best confidence interval to use since my sample size is too small for 99% confidence level and 95% confidence has a lower margin of error (increased chance of being right) than 90% confidence level.
References
Chamberlain College of Nursing (2019). MATH-225 Week 6: From Samples To Population. [Online Publication] Downers Grove, IL.
Mackowiak, P.A., Wasserman, S.S., and Levine, M.M. (1992), "A Critical Appraisal of 98.6 Degrees F, the Upper Limit of the Normal Body Temperature, and Other Legacies of Carl Reinhold August Wunderlich," Journal of the American Medical Association, 268, 1578-1580.
~JERRI BROWN
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