A cell phone manufacturer claims that the batteries in its latest model provide 20 hours of continuous use. In order to verify this claim, and independent testing firm checks the battery life of 100 phones. They find that the batteries in these 100 phones last an average of 19 hours with a standard deviation of 5 hours. Conduct an appropriate hypothesis test to check whether the results from this sample provide sufficient evidence that the true mean battery life is significantly less than 20 hours. a) Is this a question about the sample mean or the sample proportion? Explain how you know. b) What is the most appropriate test, a two-tailed test, a right-tailed test, or a left- tailed test? Explain how you know. c) State the null and alternative hypotheses. Make sure to use proper notation. d) Calculate the test statistic. Make sure to show all your computations. e) Determine the P-value. Make sure to explain how you obtained the value. f) State the decision about the null hypothesis as well as the conclusion from your hypothesis test in the context of the problem. [MP2 also]