SECTION 13.1 Exercises

For Exercises 13.1 and 13.2, see page 651; and for 13.3 and 13.4, see pages 655-656.

Question 13.5

13.5 Lag 0.

The ACF shown in Figure 13.10 (page 654) starts with lag 1. However, some software will report and plot the autocorrelation for lag 0. Regardless of the series involved, what is the value of the lag 0 autocorrelation?

13.5

1.

Question 13.6

13.6 Annual inflation rate.

Here are the annual inflation rates for the United States for the years 2000 through 2013:

Year 2000 2001 2002 2003 2004 2005 2006
Percent (%) 3.4 2.8 1.6 2.3 2.7 3.4 3.2
Year 2007 2008 2009 2010 2011 2012 2013
Percent (%) 2.8 3.8 −0.4 1.6 3.2 2.1 1.5
  1. Determine the values of and and the number of runs around the sample mean.
  2. Assuming the underlying process is random, what is the expected number of runs?
  3. Determine the -value of the hypothesis test of randomness.

Question 13.7

13.7 Runs test output.

Here is the runs test output for a time series labeled X:

Runs test for X

Runs above and below K = 200.742

The observed number of runs = 53

The expected number of runs = 44.9091
46 observations above K, 42 below
P-value = ???

  1. How many observations are in the data series?
  2. Determine the missing -value.

13.7

(a) . (b) .

Question 13.8

13.8 Randomness versus distribution.

In this section, we defined a Normal random process as being a process that generates independent observations that are well described by the Normal distribution. Consider daily data on the average waiting time (minutes) for patients at a health clinic over the course of 50 consecutive workdays.

clinic

  1. Use statistical software to make a time plot of these data. From your visual inspection of the plot, what do you conclude about the behavior of the process?
  2. Obtain an ACF for the series. What do you conclude?
  3. Use statistical software to create a histogram and a Normal quantile plot of these data. What do these plots suggest?
  4. Based on what you learned from parts (a), (b), and (c), summarize the overall nature of the clinic waiting-time process.