Consider the pooled t variable T which has a t

Chapter 9, Problem 9.34

(choose chapter or problem)

Consider the pooled t variable T which has a t distribution with m n 2 df when both population distributions are normal with 1 2 (see the Pooled t Procedures subsection for a description of Sp). a. Use this t variable to obtain a pooled t confidence interval formula for 1 2. b. A sample of ultrasonic humidifiers of one particular brand was selected for which the observations on maximum output of moisture (oz) in a controlled chamber were 14.0, 14.3, 12.2, and 15.1. A sample of the second brand gave output values 12.1, 13.6, 11.9, and 11.2 (Multiple Comparisons of Means Using Simultaneous Confidence Intervals, J. of Quality Technology, 1989: 232241). Use the pooled t formula from part (a) to estimate the difference between true average outputs for the two brands with a 95% confidence interval. c. Estimate the difference between the two s using the two-sample t interval discussed in this section, and compare it to the interval of part (b). 35.