1 A magazine conducted a survey about the sleeping time of adults. A random sample of 12 adults was chosen from the adults travelling to work on a train.
- Give a reason why this is an unsatisfactory sample for the purposes of the survey.
- State a population for which this sample would be satisfactory.
A satisfactory sample of 12 adults gave numbers of hours of sleep as shown below.
\(4.6 \quad 6.8\)
5.2
6.2
5.7
\(\begin{array} { l l } 7.1 & 6.3 \end{array}\)
5.6
7.0
\(5.8 \quad 6.5\)
7.2 - Calculate unbiased estimates of the mean and variance of the sleeping times of adults.