chapter 1

Chapter 9: Inferences Based on Two SamplesSection 9.447. H o will be rejected if ≤ −z= 2. 33z . With p ˆ1= . 150 , and ˆ 2= . 300. 01−p ,p ˆ30 + 80 210= = = .263 , and q ˆ = . 737200 + 600 800z =.150 − .300 − .150= = −4.18. Because − 4.18≤ −2.331 1.263 .737 + .0359( )( )( )200600. The calculated test statistic is, H o isrejected; the proportion of those who repeat after inducement appears lower than those whorepeat after no inducement.48.6375a. H o will be rejected if z ≥ 1. 96 . With p ˆ1= = . 2100 , and p ˆ 2= = . 4167 ,30018063 + 75.2100 − .4167 − .2067p ˆ = = .2875 , == = −4.84300 + 1801 1.2875 .7125 + .0427Since − 4.84≤ −1.96 , H o is rejected.z .( )( )( )300180b. p = . 275 and = . 0432σ , so power =[( 1.96)( .0421).2] ⎞ ⎛ [ − ( 1.96)( .0421)+ .2]⎡ ⎛ +1 − ⎢Φ⎜⎟ − Φ⎜⎣ ⎝ .0432 ⎠ ⎝1 − Φ 6.54 − Φ 2.72 = . .[ ( ) ( )] 9967.0432⎞⎤⎟⎥=⎠⎦49.1 Parameter of interest: p 1 – p 2 = true difference in proportions of those responding totwo different survey covers. Let p 1 = Plain, p 2 = Picture.2 H p − p 00:1 2=H a: p1 − p2