)
{chis quare)
A researcher in a large organization wishes to study sickness absence amongst its
employees. The organization has a large number of branches, each of each keeps full
records of sickness leave. A random sample of 10 such branches produced the following
data showing the number of sickness per branch in past one year.
18 23 26 30 32 35 39 45 48 54
Required:
a) Using the data
i) Calculate a 95% confidence interval for the mean mount of sickness days per
branch.
(6 marks)
ii) Estimate the number of branches that should be included in a simple random
sample so that 95% confidence interval for the mean number of days of sickness
should not have a width greater than four days.
(4 marks)
b) After the sample was collected, it became apparent that the branches fell into three
natural groups in terms of sales – small, medium and large. From her data on all the
branches, the researcher found that 210 randomly selected staff, 90 worked in small
branches, 36 in medium-sized branches and the rest worked in large branches. In total, 96
of the selected staff had no days off for sickness, of which 52 worked in small branches
and 29 worked in large-sized branches