Part 2: Exercising your reasoning skills The following questions might be more challenging. Many of them extend what we have discussed and do not exactly match examples presented in the textbook or in lecture. However, we still want you to wrestle through these questions and ask for clarification along the way. We hope that ultimately, working through these more challenging problems will strengthen your understanding of the big ideas behind confidence intervals. 10. What proportion smartphone users own an Android phone? A 95% confidence interval is constructed in order to estimate this unknown population proportion. The interval ends up being from 0.39 to 0.47. Based on this interval, we know the sample proportion must be and the margin of error must be