In MiniCase 10.2, we found that the mean methane gas emissions for the two pneumatic controller manufacturers were not equal. When choosing formula 10.3 to calculate the t statistic, we assumed that their variances were not equal. Was this a valid assumption? Use Cemco's sample s1 = 147.2 scfd (n1 = 18) and Invalco's sample s 2 5 237.9 scfd (n2 = 17) to find out.
(a) State the hypotheses for a two-tailed test.
(b) Calculate the critical value for 5 .10.
(c) Calculate the test statistic.
(d) What is your conclusion?