Power line outages. Use the data on the four longest power lines in Table 1.1
(a) Calculate a pooled estimate 
of their assumed common true failure rate.
(b) Calculate the test statistic (1.7). How many degrees of freedom does it have? Look up the 95 and 99% points of the corresponding chi-square distribution.
(c) Is the test statistic statistically significant? Which lines contribute significantly to the test statistic?
(d) Is the chi-square approximation adequate? Why? in Table 1.1
Table 1.1
