9.30 Fatigue behavior of reinforced concrete beams in seawater was studied by Hodgkiess et al.

(Materials Performance, July 1984, pp. 27–29).

The number of cycles to failure in seawater for beams subjected to certain bending and loading stress was as follows (in thousands):

774, 633, 477, 268, 407, 576, 659, 963, 193 Construct a 90% confidence interval estimate of the average number of cycles to failure for beams of this type.