Question 1

The table below shows an incomplete cumulative frequency distribution of some random data.

Frequency is denoted by (f) and the numeric cumulative frequency by (F).

Class intervals f F 0 -< 6 5 5 6 -< 12 9 12-< 18 4 18-< 24 5 24-< 30 5 30-< 36 2

Use the frequency table above to answer the following questions.

Complete the cumulative frequency column of the table above.

1.1 Calculate the Mean.

1.2 Calculate the Mode.

1.3 Calculate the Standard deviation.

Question 2

The queue manager at a bank believes that their clients spend, on average, less than 15 minutes in the queue. To test his belief the manager commissioned a study, which found out that, from a random sample of 80 customers, the average waiting time was 18 minutes. Assume a population standard deviation of 3 minutes and that the waiting time is approximately normally distributed.

(a) Formulate the null and the alternative hypothesis for this test situation

(b) Which test statistic (z or t) is appropriate for this test? Give a reason for your answer.

(c) Conduct a hypothesis test for a single mean at 5% significance level. Interpret your results.