Chapter 7: Statistical Data Treatment & Evaluation CHE 321: Quantitative Chemical Analysis Dr. Jerome Williams, Ph.D. Saint Leo University

Overview Statistical Testing to Data Treatment – Confidence Intervals

Statistical Testing to Data Treatment The confidence interval for the mean is the range of values within which the population mean (μ) is expected to lie with a certain probability. The confidence level is the probability that the true mean lies within a certain interval. It is often expressed as a percentage.

Statistical Testing to Data Treatment Calculating a confidence interval (CI) CI for μ = mean ± (zσ / √N ) Equation applies only if we can assume that s is a good approximation of σ.

Figure 7-1 p125

Figure 7-1a p125

Figure 7-1b p125

Figure 7-1c p125

Figure 7-1d p125

Figure 7-1e p125

Table 7-1 p125

Table 7-2 p125

Statistical Testing to Data Treatment Suppose we consider the case where s is not a good approximation of σ. To account for this, we often use the t-test. Calculating a confidence interval (CI) CI for μ = mean ± (ts / √N )

Table 7-3 p127