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Alice Ying Nie

STAT 501 Homework #9

2.18

A) From the plot we c!n le!rn th!t ! high percent o" !lcohol e$!te% to ! high percent o"

c!r&oh'(r!te%.

) From the (!t! "ile we c!n %ee th!t *+,o$l+% Anhe$%er $%ch i% the o$tlier.

-) S ATTA-H, /AHS

,) !%e( on wh!t %ee in m' %c!tterplot there i% no rel!tion%hip &etween c!r&oh'(r!te% !n( the

percent o" !lcohol.

2.23

A) The "ir%t4te%t %core %ho$l( pl!' the role o" the epl!n!tor' 6!ri!&le in (e%cri&ing thi%

rel!tion%hip.

)

-) Thi% rel!tion%hip i% %o we!k &ec!$%e the "ir%t te%t %core i% not ! goo( pre(ictor "or the "in!l

e!m %core. 7!n' other 6!ri!&le% c!n &e t!ken into con%i(er!tion %$ch !% th!t %t$(ent% who

%core lower on the "ir%t e!m %core will work !n( %t$(' h!r(er "or the "in!l e!m.

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2.25

A) The %econ(4te%t %core c!n &e !n epl!n!tor' 6!ri!&le &ec!$%e it i% clo%er to the "in!l e!m

time %o ! high %core on the %econ( te%t %ho$l( epl!in high %core% on the "in!l e!m.

)

-) From the two %c!tterplot% it (oe% not !ppe!r th!t there !re !n' rel!tion%hip% &etween the

%econ( te%t %core !n( the "in!l e!m %core%. oth rel!tion%hip% !re e$!ll' we!k.

2.28

The epl!n!tor' 6!ri!&le i% the p!rent%+ income "or college %t$(ent% !n( the re%pon%e 6!ri!&le i%

how m$ch college %t$(ent% will &orrow. The%e 6!ri!&le% !re $!ntit!ti6e. wo$l( epect !

neg!ti6e correl!tion &ec!$%e !% p!rent%+ income incre!%e wo$l( epect %t$(ent%+ (e&t to(ecree%. wo$l( epect thi% &ec!$%e the we!lthier the p!rent% the le%% %t$(ent% will pro&!&l'

h!6e to &orrow &ec!$%e p!rent% will pro&!&l' help %t$(ent% p!' "or college.

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2.29

A) The %c!tterplot (oe% %how ! po%iti6e !%%oci!tion &ec!$%e higher %t$(ent%+ will c!$%ehigher re!(ing %core%.

) There i% ! gro$p o" "o$r %t$(ent% th!t !ppe!r to &e o$tlier% &ec!$%e while the' h!6e !6er!ge %core% it !ppe!r% th!t the' h!6e 6er' low re!(ing %core%.

-) gnoring the o$tlier% it !ppe!r% th!t there i% ! po%iti6e !%%oci!tion. t i% ro$ghl' line!r &$t not

6er' %trong.

2.

/AH ATTA-H,

There i% ! %trong line!r rel!tion%hip &etween %oci!l (i%tre%% !n( &r!in !cti6it'. There (oe% not!ppe!r to &e !' o$tlier%. Ye% the (!t! (oe% %$gge%t th!t &r!in !cti6it' in the p!in region i%

(irectl' rel!te( to the (i%tre%% "rom %oci!l ecl$%ion.

2.3)

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The correl!tion i% 0.28:29 %howing ! we!k rel!tion%hip &etween !lcohol !n( c!r&oh'(r!te%.

2.3:

A)

The correl!tion &etween the%e two 6!ri!&le% i% 0.51932 %howing ! we!k rel!tion%hip &etween the

%econ( te%t !n( the "in!l e!m re%$lt%.

) think th!t the correl!tion &etween the "ir%t te%t !n( the "in!l e!m %ho$l( &e e$!l to the

correl!tion &etween the %econ( te%t !n( the "in!l e!m. Thi% i% &ec!$%e "rom the two %c!tterplot%

in the e!rlier homework pro&lem% &oth %c!tterplot% %howe( we!k correl!tion%.

2.38

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A) The correl!tion &etween the "ir%t e!m %core% !n( the "in!l e!m %core% i% 0.3088.

) Ye% m' c!lc$l!tion% %$pport the %t!tement th!t the rel!tion%hip &etween the%e two

6!ri!&le% i% we!k &ec!$%e !t 0.3 thi% i% ! 6er' we!k correl!tion.-) Ye% m' c!lc$l!tion% !gree with m' pre(iction th!t the correl!tion &etween the te%t% !n(

the e!m% !re we!k.

2.;0

A) n correl!tion% &oth 6!ri!&le% h!6e to &e $!ntit!ti6e. *cc$p!tion i% c!tegoric!l not

$!ntit!ti6e.

) -orrel!tion

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2.:3

A) S ATTA-H, /AH

The correl!tion i% 0.5212 the %h!pe i% ro$ghl' line!r &$t the correl!tion i% we!k.

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) Y> ? 1:.80; @ 0.;22

-)

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,) %$!re( i% 0.2:: %o 2:.2: percent o" the 6!ri!&ilit' in Y i% epl!ine( &' C.

) n the %c!tter plot we c!n %ee th!t correl!tion i% we!k !n( %$!re( !t 2:.2: !l%o %how%

! we!k correl!tion. So m' (!t! %how% th!t there i% ! we!k rel!tion%hip &etween 6!ri!&le !n( 6!ri!&le '.

2.:9

A)

-)

Y> ? 40.12;08 @ 0.0;0:8

%$!re( ? .::1 %o ::.1D o" the 6!ri!tion in &r!in !cti6it' !mong the%e %$&Eect%

c!n &e epl!ine( &' the %tr!ight4line rel!tion%hip with %oci!l (i%tre%% %core.

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2.102

A)

)

Thi% line i% not !n !ccept!&le %$mm!r' o" the o6er!ll p!ttern &ec!$%e the (!t! c$r6e% $p !n( the

c$r6e% (own %o it i% not ! line!r rel!tion%hip.

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-)

The %$m o" the re%i($!l% i% 0.01 %o we c!n concl$(e th!t the %$m o" the re%i($!l% i% 0 !n( th!t the

0.01 i% ! ro$n(ing error.

2.110

A)

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" we ignore the o$tlier there i% ! mo(er!te line!r rel!tion%hip %howing ! neg!ti6e !%%oci!tion

which me!n% th!t the higher the i%otope le6el the lower the %ilicon le6el.

)

ith thi% o$tlier the correl!tion i% 40.8: thi% i% ! 6er' we!k correl!tion.

itho$t the o$tlier the correl!tion i% 40.:8;;0 which i% mo(er!tel' %trong.

-)

The o$tlier i% %trongl' in"l$enti!l "or the regre%%ion line &ec!$%e we c!n %ee th!t the two gr!ph%

one with the o$tlier !n( one witho$t the o$tlier i% (r!m!tic!ll' (i""erent.