1.Taking a random sample of 35 individuals waiting to be serviced by the teller, we find that the mean waiting time was 22.0 minutes and the standard deviation was 8.0 minutes. Construct a 97% confidence interval of the mean waiting time for all individuals waiting in the service line. If an individual waited for 15 minutes, would this be considered unusually fast?

2.Travelers pay taxes for flying, car rentals and hotels. The following data represent the total travel tax (in RM) for a 3-day business trip in eight randomly selected cities.

67.81

78.69

68.99

84.36

80.24

86.14

101.27

99.29

a.Determine a point estimate for the population mean travel tax.

b.Determine a point estimate for the population variance travel tax.

c.Construct and interpret a 99% confidence interval to estimate the mean tax paid for a 3-day business trip.

d.What would you recommend to a researcher who wants to increase the precision of the interval, but does not have access to additional data?

3.A study on Telco monthly usage (RM unit) has been done among students of Applied Statistics course.

a.Select 20 data from the following data at random using EXCEL. Write the whole process of the selection.

b.Construct and interpret a 95% confidence interval to estimate the mean Telco monthly usage.

Monthly bill or topup (RM)

30

50

100

100

45

30

30

30

50

30

30

50

40

30

60

40

90

40

98

45

50

90

28

30

30

50

10

20

40

35

72

42

50

35

50

60

50

30

80

35

30

130

40

59

50

42

55

30

200

40

60

100

50

30

35

40

30

150

60

50

80

120

20

50

40

45

30

35

40

30

59

42

30

98

40

30

30

30

50

35

50

50

30

60

48