6. As part of her statistics project, Deepa decided to estimate the amount of time A-level students at her school spend on private study each week. She took a random sample of students from those studying Arts subjects, Science subjects and a mixture of Arts and Science subjects. Each student kept a record of the time they spent on private study during the third week of term.

1. Write down the name of the sampling method used by Deepa.
2. Give a reason for using this method and give one advantage this method has over simple random sampling. The results Deepa obtained are summarised in the table below.

   Type of student	Sample size	Mean number of hours
   Arts	12	12.6
   Science	12	14.1
   Mixture	8	10.2

3. Show that an estimate of the mean time spent on private study by A level students at Deepa’s school, based on these 32 students is 12.56, to 2 decimal places.
   (3 marks) The standard deviation of the time spent on private study by students at the school was 2.48 hours.
4. Assuming that the number of hours spent on private study is normally distributed, find a 95\% confidence interval for the mean time spent on private study by A level students at Deepa’s school. A member of staff at the school suggested that A level students should spend on average 12 hours each week on private study.
5. Comment on this suggestion in the light of your interval.