- Sara is investigating the variation in daily maximum gust, \(t \mathrm { kn }\), for Camborne in June and July 1987.
She used the large data set to select a sample of size 20 from the June and July data for 1987. Sara selected the first value using a random number from 1 to 4 and then selected every third value after that.
- State the sampling technique Sara used.
- From your knowledge of the large data set explain why this process may not generate a sample of size 20 .
The data Sara collected are summarised as follows
$$n = 20 \quad \sum t = 374 \quad \sum t ^ { 2 } = 7600$$
- Calculate the standard deviation.