hw_answers1 - E c o n 3 2 1 A n s w e rs H o m e w o rk 0 1...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: E c o n 3 2 1 A n s w e rs H o m e w o rk 0 1 M a rtin S c h m id t S u m m e r 2 0 1 0 E x e r c is e 2 .A .2 ( m e a n t to m a k e y o u re m e m b e r th e S a lk v a c c in e tria l a n d th in k a g a in a b o u t c o m p o s itio n o f tre a tm e n t a n d c o n tro l g r o u p s ) F re e d m a n e t a l. m e n tio n in s e c tio n 1 o f c h a p te r 1 th a t r ic h e r fa m ilie s tu r n e d o u t to b e m o re lik e ly to v o lu n te e r a n d th e ir c h ild re n w e r e m o r e lik e ly to b e in fe c te d w ith p o lio . a . L in e 1 o f ta b le s h o w s th a t p o lio ra te s in th e 2 v a c c in e g r o u p s w e r e ro u g h ly th e s a m e . A d iffe re n c e in fa m il y b a c k g ro u n d a m o n g th e 2 v a c c in e g ro u p s w o u ld h a v e re s u lte d in h ig h e r p o lio r a te s fo r th e v a c c in e g ro u p h a v in g a h ig h e r p e rc e n ta g e o f c h ild re n fr o m ric h fa m ilie s (a s s u m in g th a t o th e r p o s s ib le d iffe re n c e s a m o n g th e v a c c in e g ro u p s d o n o t o u tw e ig h th is e ffe c t ) . b . L in e 3 o f ta b le s h o w s p o lio ra te s in th e 2 n o n ‐ c o n s e n t g ro u p s w e r e ro u g h ly th e s a m e . S a m e re a s o n in g a s in a . c . L in e 2 o f ta b le s h o w s th a t p o lio ra te s in th e 2 c o n tro l g r o u p s w e r e d iffe re n t. S a m e re a s o n in g a s in a . d . L o w in c o m e p e o p le a re re la tiv e ly m o re fre q u e n t in th e n o ‐ c o n s e n t g ro u p s th a n in th e c o n s e n t g ro u p a n d a re le s s lik e ly to g e t in fe c te d b y p o lio . T h e N F IP c o n tro l g r o u p is n o t s u b je c t to c o m p o s itio n b ia s fr o m c o n s e n t a n d c o n s e q u e n tly th e re la tiv e fre q u e n c y o f r ic h p e o p le is h ig h e r . T h e d iffe r e n t v u ln e r a b ilitie s th e n e x p la in th e ra te d iffe re n c e . e . D u e to th e c o m p o s itio n b ia s re s u ltin g fro m th e c o n s e n t d e c is io n th e 2 g ro u p s d iffe r in re le v a n t c h a ra c te ris tic s . G r o u p a s s ig n m e n t th r o u g h a c h a n c e m e c h a n is m a llo w s to s p lit a p o p u la tio n in to d iffe r e n t g r o u p s a n d p r e s e r v e th e r e la tiv e c o m p o s itio n (a p a r t fr o m c h a n c e v a r ia b ility ). E x e r c is e 2 .A .5 ( m e a n t to m a k e y o u th in k a b o u t p ro b le m s w h e n s u b je c ts d o n o t a c t a s in te n d e d a n d b lu r d is tin c tio n s b e tw e e n tr e a tm e n t a n d c o n tr o l g ro u p s ) S u b je c ts w h o fo u n d o u t th a t th e y w e re ta k in g v ita m in C a n d n o t th e p la c e b o w e r e le s s lik e ly to c o n tr a c t a c o ld a n d if th e y r e c o v e re d o n e th e y re c o v e r e d m o r e q u ic k ly . T h is is th e p la c e b o e ffe c t th a t is n o rm a lly e lim in a te d th ro u g h a b lin d e d s tu d y . R e v ie w E x e r c is e 2 .2 ( m e a n t to m a k e y o u a w a re o f th e fa c t th a t y o u n e e d to a d ju s t fo r g ro u p s iz e b y u s in g ra te s ) a . T h e n u m b e r o f s to le n c a rs is a n a b s o lu te n u m b e r. A s th e r e w e r e s e e m in g ly a lo t m o re C o rv e tte s th a n Q 4 5 ’s o n th e ro a d (in 2 0 0 2 3 3 ’5 8 6 C o rv e tte s w e r e s o ld v e r s u s 8 ’0 6 5 Q 4 5 ’s ) y o u n e e d to a d ju s t fo r th is fa c t a n d u s e ra te s . C a lc u la tin g ra te s b a s e d o n th e n u m b e r o f s o ld c a rs a Q 4 5 s e e m s to b e m o re lik e ly ta rg e t fo r th ie v e s th a n a C o r v e tte . b . S a m e is s u e a s in a . c . F a ls e . T h e ra te is n o t lo w b e c a u s e th e d e n o m in a to r is la r g e , b u t is lo w b e c a u s e th e d e n o m in a to r is la rg e in c o m p a ris o n to th e n u m e ra to r. R e v ie w E x e r c is e 2 .3 ( o n c e m o re c o m p o s itio n is s u e s a n d in v a lid c o m p a r is o n o f g ro u p s ) N o . In th e S a lk tria l, th e p a re n ts w h o c o n s e n te d w e re o n th e w h o le b e tte r o ff th a n p a r e n ts w h o d id n o t c o n s e n t. T h e ir c h ild re n w e re m o re a t ris k to b e g in w ith . R e v ie w E x e r c is e 2 .4 ( a g a in c o m p o s itio n is s u e s a n d in v a lid c o m p a ris o n o f g ro u p s ) a . C o m p a rin g m e n a n d w o m e n , a s w e ll a s th e d iffe re n t a g e g ro u p s s e p a ra te ly tr ie d to c o n tr o l fo r c o n fo u n d in g d u e to g e n d e r o r s e x . b . T h is c o n c lu s io n is in v a lid . It re lie s o n a c o m p a ris o n o f g r o u p s th a t d iffe r in re le v a n t w a y s . E x ‐ s m o k e rs a r e a s e lf ‐ s e le c te d g ro u p , a n d m a n y p e o p le g iv e u p s m o k in g b e c a u s e th e y a re s ic k . T h e g ro u p o f re c e n t e x ‐ s m o k e r s c o m p ris e s a d is p ro p o rtio n a te n u m b e r o f s ic k p e o p le . R e v ie w E x e r c is e 2 .7 ( c o m p o s itio n is s u e s a n d in v a lid c o m p a ris o n o f g ro u p s ) a . O b s e rv a tio n a l s tu d y b . A g e , m a rita l s ta tu s , a n d e d u c a tio n a re p o te n tia l c o n fo u n d e rs : r a te s o f c e rv ic a l c a n c e r g o u p w ith a g e ; w o m e n o f d iffe r e n t m a r ita l s ta tu s h a v e d iffe re n t p a tte rn s o f s e x u a l a c tiv ity a n d a re e x p o s e d to d iffe r e n t k in d s o f ris k ; e d u c a tio n ra is e s s im ila r is s u e s lik e m a rita l s ta tu s . T h e re fo re , th e in v e s tig a to rs trie d to c o n tro l fo r th e s e fa c to rs . c . P ill u s e rs a re lik e ly to b e m o re s e x u a lly a c tiv e th a n n o n ‐ u s e r s a n d h a v e m o re p a rtn e rs . T h a t s e e m s to b e w h a t m a k e s th e ra te o f c e r v ic a l c a n c e r h ig h e r a m o n g p ill u s e rs . d . N o . S e e c . R e v ie w E x e r c is e 2 .1 1 a . T h e tre a tm e n t g ro u p c o m p ris e s th o s e w h o h a v e fin is h e d th e b o o t c a m p . T h e c o n tro l g ro u p c o m p ris e s o f o th e r p ris o n e r s (n o t v o lu n te e r in g o r v o lu n te e rin g a n d n o t fin is h in g th e b o o t c a m p ). b . T h e s tu d y is o b s e rv a tio n a l. T h e p ris o n e rs d e c id e w h e th e r to v o lu n te e r fo r th e b o o t c a m p a n d w h e th e r to fin is h o r n o t. T h e s e d e c is io n s c a n re s u lt in v e ry d iffe re n t c o m p o s itio n s o f th e g ro u p s th a t a re c o m p a re d B e w a r e o f p e o p le w h o d e r iv e c a u s a l c o n c lu s io n s fr o m o n e o b s e r v a tio n a l s tu d y . B e c r itic a l o f p e o p le w h o d e r iv e c a u s a l c o n c lu s io n fr o m d o z e n s o f o b s e r v a tio n a l s tu d ie s . R e v ie w E x e r c is e 3 .1 6 6 in c h e s , 7 2 in c h e s R e v ie w E x e r c is e 3 .4 a. 25% b. 99% c . 1 4 0 ‐ 1 5 0 m m d . 1 3 5 – 1 4 0 m m e . a b o u t 5 x 2 .1 = 1 0 .5 % f. 1 0 2 – 1 0 3 m m R e v ie w E x e r c is e 4 .1 a . a v e ra g e = 5 0 , d e v ia tio n s = ‐ 9 , ‐ 2 , 0 , 0 , 4 , 7 , S D = 5 b . 4 8 , 5 0 , 5 0 w ith in 0 5 S D ’s o f a v e ra g e , i.e . in th e ra n g e fr o m 4 7 .5 to 5 2 .5 ; 4 8 , 5 0 , 5 0 , 5 4 , 5 7 a re w ith in 1 .5 S D ’s o f a v e ra g e , i.e . in th e ra n g e fro m 4 2 .5 to 5 7 .5 ...
View Full Document

Ask a homework question - tutors are online