4.48    If the number of hurricanes that hit a certain area of the eastern United States per year is a random variable having a Poisson distribution with μ = 6, find the probability that this area will be hit by

(a)   exactly 15 hurricanes in 2 years;

(b)   at most 9 hurricanes in 2 years.

 

4.49    The following data represent the length of life in years, measured to the nearest tenth, of 30 similar fuel pumps:

 

t = x¯      − 53, 000

√

s/  10

and determine from Table A.4 (with 9 degrees of free- dom) whether the computed t-value is reasonable or appears to be a rare   event.

 

4.54 Two distinct solid fuel propellants, type A and type B, are being considered for a space program activ- ity. Burning rates of the propellant are crucial. Ran- dom samples of 20 specimens of the two propellants

 

2.0	3.0	0.3	3.3	1.3	0.4	are taken with sample means 20.5 cm/sec for propel-
0.2	6.0	5.5	6.5	0.2	2.3	lant  A and  24.50  cm/sec  for  propellant  B.  It  is gen-
1.5	4.0	5.9	1.8	4.7	0.7	erally assumed that the variability in burning rate is
4.5	0.3	1.5	0.5	2.5	5.0	roughly the same for the two propellants and is   given
1.0	6.0	5.6	6.0	1.2	0.2	by  a population standard deviation of 5 cm/sec.     As-

 

Construct a box-and-whisker plot. Comment on the outliers in the  data.