P-Values and Confidence Intervals in Epidemiology, Coursework Example

The role of p-values and confidence intervals within epidemiologic research is identified here and an example of how these are used to interpret research findings is presented. Furthermore, the effect of sample size on p-values, confidence intervals, and interpretation of statistical results is discussed.

First, the role of p-values and confidence intervals within epidemiologic research is identified here and an example of how these are used to interpret research findings is presented. A confidence interval is used to approximate the effect of a condition such as a treatment (Davies & Crombie, 2009). It defines the range within the treatment or condition are believed be most likely effective (Davies & Crombie, 2009). For example, researchers were 95% sure of the impact of plasma homocysteine concentrations and extra cranial carotid-artery stenosis within the range of 1.4 and 4.9 (Selhub et. al., 1995). The p-value is a measure whether the treatment or condition is likely to be attributable to mere chance (Davies & Crombie, 2009). For example, researchers believed there was a less than a .01% chance that the effect was attributable to chance (Selhub et. al., 1995).

Next, the effect of sample size on p-values, confidence intervals, and interpretation of statistical results is discussed. For p-values, sample sizes are taken into account during calculation. Thus, there is no effect of sample size on p-values, but for confidence intervals, the larger the sample the more accurate the calculation. Nevertheless, a large sample size and a small confidence interval can be misinterpreted due to statistical bias (Davies & Crombie, 2009).

The role of p-values and confidence intervals within epidemiologic research has been identified here and an example of how these are used to interpret research findings presented. Furthermore, the effect of sample size on p-values, confidence intervals, and interpretation of statistical results has been discussed.

References

Davies, H.T. & Crombie, I.K. (2009). What is…?series: What are confidence intervals and p-values? Hayward Group Ltd.

Selhub, J. et. al. (1995). Association between plasma homocysteine concentrations and extra cranial carotid-artery stenosis. New England Journal of Medicine: 286-291.