Moderate -0.8 This is a straightforward application of the large-sample confidence interval formula with all values provided. Students simply need to recall z* = 2.326 for 98% confidence and substitute into x̄ ± z*√(s²/n). No conceptual challenges or multi-step reasoning required—purely mechanical calculation, making it easier than average.
The time taken for a particular type of paint to dry was measured for a sample of 150 randomly chosen points on a wall. The sample mean was 192.4 minutes and an unbiased estimate of the population variance was 43.6 minutes\(^2\). Find a 98\% confidence interval for the mean drying time. [3]
The time taken for a particular type of paint to dry was measured for a sample of 150 randomly chosen points on a wall. The sample mean was 192.4 minutes and an unbiased estimate of the population variance was 43.6 minutes$^2$. Find a 98\% confidence interval for the mean drying time. [3]
\hfill \mbox{\textit{CAIE S2 2016 Q1 [3]}}