Moderate -0.8 This is a straightforward confidence interval calculation requiring only direct substitution into the standard formula with given values (sample mean, variance, and sample size). The large sample size (n=120) means students can use the normal distribution without concern, and all necessary information is provided explicitly. This is simpler than average A-level questions as it involves no problem-solving, just mechanical application of a memorized procedure.
The time taken, \(T\) minutes, for a special anti-rust paint to dry was measured for a random sample of 120 painted pieces of metal. The sample mean was 51.2 minutes and an unbiased estimate of the population variance was 37.4 minutes\(^2\). Determine a 99% confidence interval for the mean drying time. [3]
The time taken, $T$ minutes, for a special anti-rust paint to dry was measured for a random sample of 120 painted pieces of metal. The sample mean was 51.2 minutes and an unbiased estimate of the population variance was 37.4 minutes$^2$. Determine a 99% confidence interval for the mean drying time. [3]
\hfill \mbox{\textit{CAIE S2 2002 Q1 [3]}}