Two types of phone operating system are being tested to determine if there is a difference in the proportions of system failures (crashes). fifteen out of a random sample of 150 phones with os1 had system failures within the first eight hours of operation. ten out of another random sample of 150 phones with os2 had system failures within the first eight hours of operation. os2 is believed to be more stable (have fewer crashes) than os1.

(b) suppose that consolidated power decides to use a level of significance of α = .05, and suppose a random sample of 100 temperature readings is obtained. if the sample mean of the 100 temperature readings is x⎯⎯ = 60.990, test h0 versus ha and determine whether the power plant should be shut down and the cooling system repaired. perform the hypothesis test by using a critical value and a p-value. assume σ = 5. (round your z to 2 decimal places and p-value to 4 decimal places.)