3 The heights, in metres, of a random sample of 10 students attending Higrade School are recorded below.
\(\begin{array} { l l l l l l l l l } 1.76 & 1.59 & 1.54 & 1.62 & 1.49 & 1.52 & 1.56 & 1.47 & 1.75 \end{array} 1.50\) Assume that the heights of students attending Higrade School are normally distributed.

1. Calculate unbiased estimates for the mean and variance of the heights of students attending Higrade School.
   (3 marks)
2. Construct a 90\% confidence interval for the mean height of students attending Higrade School.
   (5 marks)