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71 1

0361- 803X/94 /1633- 0711 A m e ric an R oe n tg en R ay S oc ie ty

U se o f S ta tis tic a l A na lys is in th eA JR a n d Rad io logy : F requency ,M e thods , and Subspec ia lty D iffe ren ces

A llen D . E ls te r1

R ec e iv ed A p n l 11 , 1 9 94 ; a cc ep ted a fte r rev is ionM ay 1 3 , 1 99 4 .S up po rte d by a M e lv in M . F ig le y fe llow sh ip in ra -

d io lo g ic j ou rn a li sm .1 D ep artm en t o f R a d io log y , B o w m an G ray

S ch oo l o f M ed ic ine , W ake F ores t U n iv e rs ity , M ed i-ca l C e n te r B lv d ., W ins ton -S a le m , N C 27 1 5 7-102 2 .Addr es s co rre spo nde nc e to A . D . E ls ten .

OBJECT IVE . Th e s tatis tica l p rocedures appear ing in Rad io logy and th e A JR werean a lyzed to de te rm in e the types o f s ta tis tica l tes ts u sed in m ajo r a rtic les , th e ir re la tivefre quenc ies , and w he th e r th e se m e thods d if fe red acco rd ing to rad io lo g ic subspec ia lty .

MATER IA LS AND M ETHODS . S ix hund red s ix ty -n ine m a jo r a rtic les pub lished inRad io logy o r th e A JR dur in g I 9 93 w e re re v iew ed fo r s ta tis tic a l con ten t. T h ese a rtic lesw ere firs t c lass if ied by rad io log ic sub sp ec ia lty o r p rinc ip a l fo cus accord ing to th enam ed jou rn a l s e c tio n w he re each appea red (e .g ., b re as t im ag ing , m uscu lo ske le ta lrad io lo g y , n eu ro rad io lo g y). T h e s ta tis tica l m e thods used in each a rtic le w ere th enass ig ned to on e o f 1 8 ca tego ries (e .g ., desc rip tive , bas ic t- an d z-tes ts , co rre la tio n !reg ress ion te chn iques , and nonparam etric s ta tis tic s ).

R ESU LTS . O f th e 669 m ajo r a rtic les an a lyzed , 2 9 4 (4 4 % ) u sed no s ta tis tica l m eth od so r d esc rip tiv e s ta t is tics on ly , 1 7 9 (2 7% ) used on ly one type o f s ta tis tic a l m e thod , 1 02(15% ) u sed tw o m ethods , and 94 (14% ) used th ree o r m ore m e thods . S ta tis tica l tech -n iques w e re m ost lik e ly to b e used in a rtic les c las s ifie d as card iac (8 5% used s ta tis ti-ca l ana lys is ) o r con tras t ag en ts (79% ), b u t leas t like ly to be used in gas tro in tes tina l!a b d o m in a l im a g in g (4 5 % ), ra d io th e ra p y (4 4 % ), o r m isce llan eou s top ics (29% ). F iveb as ic ca tego ries o f s ta tis tica l m ethod s-b asic z- and t-tes ts , bas ic d ec is io n s ta tis tics(s ens itiv ity , sp ec ific ity ), bas ic con ting enc y tab le an aly sis 2 , M cN em a r), co rre la t ion !reg ress ion te chn iques ( lin e ar reg re ss ion , P ea rson coe ffic ie n ts ), and bas ic nonpa ra -m etric tes ts (W ilc o xon , M ann-W h itne y U )-a c coun t fo r th e com p le te s ta tis tic a l a n a ly -s is a ppe arin g in ap p rox im ate ly 80 % o f the m ajo r a rtic les .

CONCLUS ION . A pp rox im ate ly h a lf th e m ajo r a rtic les appea rin g in Rad io logy o r AJ Rused no s ta tis tics , desc rip tive an a lys is on ly , o r a s im p le in fe ren tia l tes t em plo y ing t-tes ts o r con fiden ce in te rva ls ; ad vanced s ta tis tica l techn iqu es w ere fo und in on ly 20%o f a rtic les . S ta tis tica l an a lys is w as m ost lik e ly to b e used in ar tic le s d ea lin g w ith c ar -d ia c rad io lo g y o r con tra s t ag en ts and le as t like ly to b e used in a rtic le s on abdom in a l!g a s tro in te s tin a l rad io lo g y , rad io th e rap y , and m is ce llan eous rad io lo g ic top ic s .

A JR 1994;163 :711 -715

S ta tis tic a l p ro c ed u re s a re a p p e a rin g w ith in c re a s in g fre q u e n cy in m e d ica l p u b li-ca tio n s , a tre n d w ith m ixe d b le s s in g s th at h a s re ce n tly re ce ive d e d ito ria l a tte n tio n[1-6 ] . T h e ris in g num be r a nd c om p le x ity o f s ta tis tic a l m e th ods u se d in m e d ic a ljo u rn a ls co n tra s ts sh a rp ly w ith th e lo w le ve l o f s ta tis tic a l kn o w le d g e h e ld b y th eav e rag e p hys ic ian [7 -9 ]. T h is p ro life ra tion o f s ta tis tic s in m ed ica l pub lic a tionsp o te n tia lly m a k e s sc ie n tific s tu d ie s m o re d iffic u lt fo r th e g e n e ra l re a d e r to co m p re -h e n d fu lly . C o n se q u e n tly , au th o rs , re fe re e s , a n d e d ito rs a ll h a v e an in cre a se dre s p o n s ib ility to e n su re th e ac cu ra cy a nd p e rtin e n ce o f th e s ta tis tica l te s ts th eyus e , rev iew , o r pub lis h .

A ltho u g h th e s ta tis tica l c o n te n t o f se ve ra l no n ra d io lo g ic m e d ica l jo u rn a ls h a sb e e n re p o rte d in re c e n t ye a rs [1 0 -33 ], n o s im ila r e va lu a tio ns o f n ad io lo g ic p u b lica -tio n s h av e ye t a p p e are d . T h e re fo re , a rtic le s p u b lish e d in Rad io logy and the AJRin a 1 -ye a r p e rio d w e re re v ie w e d to d e te rm in e th e n u m b e rs a n d ty p e s o f s ta tis tica lte s ts u se d . I a lso w a n te d to d e te rm in e w h e th e r th e u s e o f s ta tis tic a l m e th o d s va r-ie d a c co rd in g to ra d io lo g ic su b s p e c ia lty , a nd h o w th e o ve ra ll u se o f th e s e m e th -

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E a c h a rtic le w a s the n re v ie w e d to d e te rm in e th e typ e s o f s ta tis ti-ca l m e th od s it co n ta in e d . T he m e tho d s fo u nd in e ach a rtic le w e rea ss ig n e d to o n e o f 1 8 ca te g o rie s (T a b le 2 ). (A s in g le a rtic le c o u ldh a v e u s ed s ta tis tica l p ro c e d u re s fro m o n e o r m ore o f th e se c a te go -

TA BLE 2 : C lass if ica tio n o f S ta tis tica l P rocedures

ods in Rad io logy an d AJR co m p a re d w ith th a t in o th e rg e n e ra l m e d ic a l a n d su rg ic a l jo u rn a ls .

M ate ria ls and M e thod sT h e a rtic le s re v ie w e d fo r th is s tu d y w e re a ll p u b lish e d b e tw e e n

Ja n u a ry a n d D e c em b e r 1 9 9 3 e ith e r in Rad io logy (vo lu m es 1 8 6 -1 8 9 ) o r th e AJR (vo lu m e s 1 60 an d 1 6 1 ). S u p p le m e n ta ry is su e s o fe a ch jo u rn a l p u b lish e d d u rin g th is p e r io d c o n ta in in g a b s tra c ts o f th ea n n u a l m ee tin gs o f th e A m erica n R o e n tg e n R a y S o c ie ty a n d R a d io -lo g ica l S o c ie ty o f N orth A m erica w ere n o t in c lu d e d in th e a n a lys is .

T h e a rtic le s ch o se n fo r re v ie w w e re e x c lu s ive ly m a jo r p a p e rs ,o p e ra tio n a lly d e fin e d to b e o rig in a l re p o rts d e scr ib in g im ag in g find -in g s in a t le a s t 10 p a tie n ts o r e xp e rim en ta l s tu d ie s in w h ic h a t le a s tI 0 m e a s u re m e n ts o r n u m e ric d a ta o f a n y k in d h a d be e n o b ta in e d .A ll o th e r a rtic le s , in c lu d in g te c h n ica l n o te s , c a se re p o rts (fe w er th a n1 0 p a tie n ts ), p ic to ria l e ss a ys , re v ie w a rtic le s , e d ito r ia ls , le tte rs , a n dn e w s ite m s, w ere e xc lu d e d fro m th is a n a ly s is .

E a c h m ajo r p a p e r w as f i rs t ca te go rize d b y o rg an sy ste m o r ra dio lo gicsubspec ia l ty a c co rd in g to its o r ig in a l a ss ig n m en t in a jou rn a l s e c tio n(T ab le 1 ). T o r e d uc e f ra g m e n t a ti o n in to to o m an y sm all ca te go rie s, so medose ly re la ted s ub jec ts (su ch a s h ea d an d n e ck rad io logy an d n e u n o ra d i -o lo gy ) w ere gr ouped to ge th er u nd er a s in gle h ea din g. S ub sp ec ia lty s ec-tio ns (s uc h as ly mp hog raphy , co mpu te r a pp lica tion s, a nd m ed ica lp hys ics ) in w hic h fe we r th an 1 0 m ajo r a rtid es o fe a ch ty pe h ad b ee n pub-l ished o ve r th e y ea r were co llap se d in to a s ing le misce l laneous c a tego r y .

TA BLE 1 : C lassif ica tio n o f A rtic les b y S ubsp ec la lty !S ec tio n

C a te g o ry D e scr ip tio nN o s ta tis tica l p ro c e d u re s e m plo ye d o r s ta tis ti-

ca l in fe re nc es m ad e; d es crip tive s ta tis tic so nly ( e.g . , m ea ns, p erc en ta ge s, s ta nd arde rr o rs , h is to g ra m s )

S en s itiv ity , spe c if ic ity , p os itiv e p re d ic tiv ev alu e, a cc ur ac y

A d v a n ce d R e la tiv e r isk , o d d s ra tio , lo g o d d s ; b a ye s ia ne stim atio n; B erkso ns a na lys is

R O C A d va n ce d d e c is io n s ta tis tics b a s e d o na n a lys is o f R O C cu rve s

B a s ic t- an d z-tes ts O n e-s am p le , m a tch ed -p a ir, an d tw o -sa m p let- te sts a nd z-te sts ; c on fid en ce in te rv alsP ow er a na lys is ; sa m ple s ize e s tim atio n ;

s en sitiv ity a na ly sis ; m eta -a na ly sis2 -te s ts , F ish e rs exa c t tes t, M c N e m a r te s tM ultiw ay ta b le s ; M an te l-H ae n s ze l te s t, lo g -

lin ea r m od elsCorre la t ion /regress ion

B a s ic P e a rso n c o rre la tio n c o e ffic ie n t a n d te s tin g ,tw o-v aria ble (s im ple lin ea r) reg re ss io n,le as t- sq ua re s m o de lin g

N on p a ra m etric S p e a rm an s p , K e n d a lls t; te sts fo r tre nd ;m o no to ne re gr es sio nA d v a n ce d M u ltip le lin e a r re g re s s io n ; p o lyn o m in a lre gre ss ion ; n on lin ea r reg re ss io n, e stim a-

tio n , an d m o de lin g; s te pw is e re gr es sio n;lo g is tic re g re ss ion ; d iscn im in an t a na lys is

S in g le a n d re p e a te d m eas u re s o n e -w ayA N OV A; m ultip le c om pa ris on p ro ce du re s(e .g . , N ew ma n -K eu ls , B on fe rro n i, T uke y ,D un ca n te sts ); s im ple lin ea r c on tra sts ;F- tes ts

A d va n c e d M u ltiw a y A N O V A o r a n a lys is o f c o va n ia n c e;b lo ck d eig ns (e .g ., L atin sq ua re , fa cto ria l)N o n p a ra me tn ic

B a s ic S ig n te s t, W ilco x o n s ig n e d -ra n k te s t, M a n n -W hitne y U -tes t; m e d ian /ran g e tes tA dva nc ed N on param etn ic A N O V A (K ru ska l-W a llis ,

F r iedman te s ts ); go od n ess -o f-fit te s ts(K olm og o ro v-S mim ov typ e )

Sur v iv a l a n a lys is L ife ta b le (s urv iva l fu n c tio n , K ap la n -M eie rp ro d u c t lim it a n a lys is ) , re g re ss io n fo rs urv iv al ( Ma nte l-C ox ) p ro po rtio na l ha za rdsm o de ls , r ate a dju stm en t

T ra n s fo rm a tio n U se o f d a ta tran s fo rm a tio n (e .g . , logar i thmic ,e xp on en tia l, r ec ip ro ca l)

O th e r A n y s ta tis tic a l m e th o d n o t fittin g th e a b o v eh ea din gs (e .g . , c lu s te r an a ly s is , a u to co rne -la tio n, q ua lity co ntro l ch arts , p ha rm aco ki-ne t ic mode l ing )

C la ss ifica tio n S e ctio n a ss ig n e d inRad io logyS e ctio n a ss ig n e d in

AJRA b d o m in a l A b d o m in a l a n d G a stro - G a stro in te s tin a lin te st in al R a di olo gy R a d io lo g yB re a s t B re a s t Im ag in g B rea s t R ad io lo gyC a rd ia c C a rd ia c R a d io lo g y C a rd ia c R a d io lo g yC h e s t T h o ra c ic R a d io lo g y C h e s t R a d io lo g y

Card iopu lmonaryR a d io lo g yP ulm o na ry R ad io lo gyC o n tra s t C o n tra s t M e d ia C o n tra s t M e d iaG en ito u n in a ry G en ito u r in a ry R a d io lo g y G en ito u r in a ry R ad io lo g yO bste tr ica l U ltra so u n d O bste tr ic a l R ad io lo g yIn te rve n tion a l In te rve n tion a l R a d io lo gy In te rve n tion a l R a d io lo gyM us cu lo sk ele ta l M us cu lo sk ele ta l Muscu loske le ta lR a d io lo g y R a d io lo g yS ke le ta l R a di olo gyN eu ro ra dio lo gy N eu ro ra dio lo gy N e u ro ra d io lo g yH e a d a n d N ec k H e a d a n d N e ck

Rad io logy Rad io logyP e d ia tr ic P e d ia tric R a d io lo g y P e d ia tric R a d io lo g yP re na ta l R a di olo gy

F e ta l R a dio lo gyR a d io th era p y T h e ra p e u tic R a d io lo g y ( N o t a p pl ic a bl e)V a sc u la r C a rd io v a scu la r V a s c u la r

R a d io log y R a d io lo gyM isc e lla n e o u s C om pu te r A pp lic a tio n s C om pu te rs in R ad io lo gyU ltra s o un d O n co lo g ic R a d io lo g yM e dic al P hy sic s E nd oc rin e R ad io lo gyN uc le ar M ed ic in e N u cl ea r R a di olo gyM a gn etic R es on an ce L y mp h o g ra p h y

Imag ingL ym ph atic Im ag in g N o t e . - R O C = rec e iv e r -op e ra tin g c ha rac te r is tics , A NO VA = a na lys is o f

712 E LS T E R A JR :1 63 , S ep tem be r 1 994

v a r ianc e .

None /desc r ip t ive

D e cis io n s ta ti st ic sBas ic

S tu d y d e s ig n a n dana lys isC on tin ge ncy tab le s

Bas icA d v a n c e d

ANOVAB a s ic

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A JR :1 6 3 , S ep te m be r 1 99 3 S T A T IS T IC A L A N A LY S IS IN AJR A N D RAD IOLOGY 71 3

n ie s .) A lth o u g h a d m itte d ly a rb itra ry , th e se 1 8 c ate g o rie s a re c o n s is -te n t w ith th e d iv is ion in to ch a p te rs o f m any s ta tis tica l te x tb o o ks a n dar e s im ila r to tho se u se d b y E m ers on a nd C o ld itz [1 0 ] in the ir lan d -m a rk 1 9 8 3 a rtic le e va lu a tin g s ta tis tica l p ro ce d u re s in th e NewE ng land Jou rna l o f M ed ic ine .

Resu l tsO f th e 669 m a jo r a rtic les ana lyz ed , 29 4 (4 4% ) u sed no

s ta tis tic a l m e th o d s o r d e scr ip tiv e s ta tis tics o n ly , 1 7 9 (2 7 % )us ed on ly one ty pe o f s ta tis tica l m e tho d , 1 02 (15 % ) us ed tw om e th o d s , a n d 9 4 (1 4 % ) u se d th re e o r m o re m e th o d s . B a s ic s ta tis tic s d e a lin g w ith in fe re n ce , d e c is io n s , co n tin g e n c yta b le s , o n co rre la tio n /re g re ss io n te ch n iq u e s w e re fo u n d inm o re th a n h a lf the a rtic le s in w h ich a s ta tis tica l p ro ce d u rehad b een us ed (T ab le 3 ). T he lis ting o f s ta tis tica l tes ts inT a b le 3 is g ive n in th e o rd e r o f th e ir d e cre a s in g u sa g e in th eart ic les an a ly ze d . (T h is o rde rin g is no t in ten ded to rep re sen ta rec om m en ded on op tim ized seq uen ce fo r lea rn ing ab ou tth es e s ta tis tic al p ro ce du re s.)

A ls o in c lu ded in T ab le 3 is th e co lum n C um u la tiv e A c ces -s ib ility b y M e th o d . C u m u la tive a cc e ss ib ility is d e fin e d a s th ep e rc e n ta ge o f a rtic le s to w h ic h a re a d e r w o u ld h a ve fu lla cc es s b y b e in g fa m ilia r w ith a g iv e n s ta tis tic a l p ro ce d u re a sw e ll as a ll o th e rs h ighe r up in the lis t. T he cu m u la tiv e acc es -s ib ility va lu e ta ke s in to a cco u n t th e fa c t th a t m a n y a rtic le sc on ta ine d m o re th an on e s ta tis tica l m e tho d , an d th a t s om ea rtic le s c o nta in e d a m ix tu re o f s im p le a n d a d va n c e d m e th -ods . F o r ex am p le , it c an be se en fro m T ab le 3 tha t 4 4% o f

TABLE 3 : S ta tis tica l C on ten t b y C a tegory and Access ib ility

S ta tis tic al C a te go ry N o. (% ) of A rtic le sC on ta in in g M eth od s(n = 6 6 9 )

C u mu la t i v eA cc ess ib ility b y

M eth o d (% )N o n e /d e scr ip tiv e 2 9 4 (4 4 ) 4 4B a s ic t- a n d z-te s ts 1 5 7 (2 3 ) 5 2C o n tin g e n cy ta b le s : b a s ic 1 0 6 (1 6 ) 6 0D e c is io n s ta tis tics : b a s ic 9 8 (1 5 ) 6 7C orre la tio n /reg re ss io n : b as ic 56 (8 ) 73N o n p a ra m e tn ic : b a s ic 5 1 (8 ) 8 0A n a lys is o f va r ia n ce 3 7 (6 ) 8 3(A NO VA ): b a s icC orre la tio n /re g ress ion : no n - 29 (4 ) 8 5p a ra me t r i cD e c is io n s ta tis tic s : re ce iv e r- 2 1 (3 ) 86o p er a ti ng c h ar a ct er is ti csTrans format ion 16 (2 ) 87Corre la t ion /regress ion : 1 6 (2 ) 8 8

advancedD e c is io n s ta ti st ic s: 1 4 (2 ) 9 0a d v a n c e dC o n tin g e n cy ta b le s : 13 (2 ) 9 1

a d v a n c e dN o n p a ra m e tn ic : a d v a n ce d 12 (2 ) 92S u rv iva l a n a lys is 12 (2 ) 9 4S tu d y d e s ig n a n d a n a lys is 8 (1 ) 9 6A N OV A: a dv an ce d 5 (1 ) 97O th e r 1 8 (3 ) 1 0 0

a rtic le s co n ta in e d n o s ta tis tic s a n d th a t 2 3 % o f a rtic le s c o n -ta m e d b a s ic t- a n d z-te s ts . H o w e ve r, a re a d e r fa m ilia r onlyw ith b a s ic t- a n d z-te s ts w o u ld n o t n e ce ss a rily b e a b le tou n d e rs ta n d th e s ta tis tics in 6 7 % (4 4 % + 2 3% ) o f the a rt ic les ,be ca use som e o f the inc rem e n ta l 2 3% o f a rtic les co n ta in ingb a s ic t- a n d z-te s ts a ls o co n ta in e d m o re c om ple x m etho dsfo u n d fu rth e r d ow n th e lis t w ith w h ic h th e re a d e r m ig h t n o tb e fa m ilia r . T h e cu m u la tive a c ce ss ib ility c o lu m n ta k e s th isin to a cc o u n t; h e re w e se e th a t a re a d er fa m ilia r o n ly w ithd e sc rip tive a n a lys is a n d b a s ic t- an d z-tes ts c ou ld u n d e r-s ta n d fu lly ( fro m a sta tis tic a l s ta nd p o in t) 5 2 % o f th e a rtic le sin bo th jo urna ls .

C o m p a ris o n o f m e th o d s b y ra d io lo g ic su b sp e c ia lty (T a b le 4 )sh o w s th a t s ta tis tic a l te ch n iq u e s w e re mos t like ly to b e fo u n din artic le s d e a lin g w ith c a rd ia c ra d io lo g y (8 5 % o f a rtic le s u se ds ta tis tic s ), c o n tra s t a g e n ts (7 9% ), g e n ito u r in a ry ra d io lo g y(67% ), an d in te rven tiona l rad io logy (67 % ). S ta tis tic a l tec h -n iq u e s w e re leas t like ly to b e u se d in a rtic le s d ea lin g w itha b d o m in a l ra d io lo g y (4 5 % u s e sta tis tic s ), ra d io th e ra p y (4 4 % ),on m is ce lla neo us top ics (29% ).

A d va n c e d s ta tis tica l m e th o d s ( i.e ., a ll m e th o d s n o t la b e ledas bas ic in T ab le 2 ) w ere m o stlike ly to be us ed in a rtic les dea l-in g w ith co n tra s t a g e n ts (3 6 % ) o r ra d io th e ra p y (3 1 % ); th e yw e re leas t like ly to b e u se d in a rtic le s c la ss ifie d a s a b d o m in a l(13% ) on m isc e llane ous (1 3% ). S om e cluste rin g o f adv anc eds ta tis tic a l te ch n iq ue s b y ra d io lo g ic su b sp e c ia lty w a s a lson ote d . R e ce ive r-o p e ra tin g -c h a ra c te r is tic (R O C) c u rv e a n a ly s isw a s m o st w id e ly u se d in ch e s t a n d m u scu lo ske le ta l ra d io log y ,n on p a ra m e tric c o rre la tio n te c hn iq u e s w e re m o st p ro m ine n t inn eu ro ra d io lo g y a n d m u s cu lo sk e le ta l ra d io lo g y , a n d su rv iva la n a lys is w a s p rin c ip a lly u se d in a rtic les o n ra d io th e ra p y a n dva s cu la r a n d in te rve n tio n a l ra d io lo gy .

Dis cuss ionA dram atic in cre ase ha s oc cu rre d in the n um b er an d c o rn -

p le x ity o f s ta tis tic a l m etho ds app earing in m e d ic a l pu b lica -tio n s [1 -6 , 1 0 ]. S e v e ra l e xp la n a tio n s ca n b e a d va n c ed toe xp la in th is p h e n o m e n o n , in c lu d in g (1 ) th e rec o g n itio n th a to b je c tive e v a lu a tio n o f e xp e rim e n ta l d a ta h a s m erit; (2 ) th ein s is te n ce o f m e d ica l e d ito rs a n d re fe re e s th a t fo rm al s ta tis -tic a l a n a lys e s b e inc lu d e d in m a n u s crip ts [3 , 4 ]; (3 ) th e w id e -sp re a d a v a ila b ility o f u s e r-frien d ly s ta tis tic s p ro g ra m s o np e rs o n a l c om p u te rs , a llo w in g p e rs o n s u n tra in e d in fo rm als ta tis tic a l m e th o d s to g e n e ra te co m p lex (b u t n o t n e c e ssa r ilyco rrec t) a n a ly se s o f th e ir d a ta [2 ]; a n d (4 ) th e u n in te n tio n a lb ias o f m an y jou rn a ls to p re fe ren tia lly ac ce p t p apers th a tsh o w s ta tis tica lly s ig n ifica n t re su lts , a p h e n o m e n o n fo rc in ga u th o rs to q u e s t fo r p va lu e s [3 4 , 3 5 ].

In co m p a riso n w ith o th e r m e d ic a l jo u rn a ls , th e p e rc e nta g eo f a rtic les in Rad io logy an d A JR th a t us e s ta t is t ica l an a ly s is(56 % ) c an be cons ide red av e rage . R es earc he rs rev ie w ingth e pu b lica tio n s o f o th e r m e d ic a l sp e c ia ltie s w ith in th e p a s tde ca de ha ve rep o rte d the fo llo w ing pe rcen tag es o f m a jo ra rtic le s th a t in co rp o ra te m e th o d s b e yo n d s im p le d e sc rip tives ta t is t ics : Jou rna l o f B one and Jo in t S u rge ry (B ritis h v olu m e),36 % [1 6 ]; e igh t o to la ry ngo log y jou rna ls , co ns ide re d in agg re -

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7 1 4 E L S T E R A JR :16 3 , S ep tem be r 19 94

TABLE 4 : D is tribu tio n and C om plex ity o f S ta tis tica l M eth od s A ccord in g to R ad io log ic Subspecia lty C lass ifica tion

Class if icat ion o ta o Art ic lesN o. (% ) o f A rtic les U sin g

M os t F re q u e n tly U s e dA d van ce d S ta tis tic a l M e tho ds( o . o rtic e s)N o S ta tis tic s o r

Sta t icsOn lM ore T ha n O ne

M e t h o dAdv anc ed

M e t h o d sA b d o m in a l 1 1 6 6 4 ( 55 ) 2 7 ( 2 3 ) 1 5 (1 3 ) N o np a ra m e tn ic , a d v an c e d (3 ); c o rre la tio n /

reg re ss ion , n o np aram etn ic (3 )B re a s t 4 1 2 0 (49 ) 1 1 (2 7 ) 7 (1 7 ) C o rre la tio n /re g res s io n , a d v a n ce d (3 )C a rd ia c 2 0 3 (15 ) 7 (3 5 ) 5 (2 5 )C h e st 8 3 3 4 (41 ) 3 2 (3 9 ) 1 4 (1 7 ) D e c is io n , R O C (7 )C o n tra s t 1 4 3 (21 ) 7 (5 0 ) 5 (3 6 ) S tu d y d e s ig n (2 ); A N O V A , a d v a n ce d (2 )G en itou n in a ry 70 23 (33 ) 2 3 (3 3 ) 1 3 (1 9 ) D e c is io n , a d v a n ce d (4 ); co rre la tio n /re g re s s io n , n o n p a ra m etn ic (3 )I n te r v en t iona l 2 7 9 (33 ) 6 (22 ) 6 ( 22 ) Su rv iva l a na lys is (3 )M is ce lla n e o us 2 4 1 7 (71 ) 3 (1 3 ) 3 (1 3 )M u sc u lo sk e le ta l 8 3 4 0 (4 8 ) 2 5 ( 3 0 ) 1 6 ( 1 9 ) C o rre la tio n /re g re ss io n , n o n p a ram e tn ic (5 );

d ec is io n , R O C (4 )N e u ro ra d io lo g y 8 0 3 1 (39 ) 2 0 (2 5 ) 2 0 (2 5 ) C orre la tio n/re gres sio n, n on pa ram etn ic (3 );

t ran s fo rm a tion (6 )P e d ia tr ic 5 1 2 1 (41 ) 1 7 (3 3 ) 8 (1 6 ) C o rre la tio n /re g re ss io n , a d v a n ce d (4 );

tra n s fo rm atio n (4 )R a d io th e rap y 16 9 (5 6 ) 3 (19 ) 5 (31 ) S u rv iva l an a lys is (4 )V a s c u la r

Tota ls4 4 2 0 (4 5 ) 1 5 (3 4 ) 1 1 (2 5 ) S u rv iv a l a n a lys is (4 )

6 6 9 2 9 4 (4 4 ) 1 9 6 (2 9 ) 1 28 (1 9 )N o t e . - R O C = re ce ive r-o pe ra ting ch ara cte ris tics , A NO VA = a na ly sis o f va ria nc e.

g a te , 3 7 % [3 2 ]; Jou rna l o f Fam ily P rac tic e , 4 1 % [1 3 ]; Pedia t-r ics , 4 2 % [1 1 ]; 1 6 p a th o lo g y jo u rn a ls , s tu d ie d in a g g re g a te ,4 9 % [3 0 ]; Am erican Jou rna l o f O ccupa tiona l T he rapy , 50 %[29]; Am erican Jou rna l o f T rop ica l M ed ic ine and Hyg iene ,6 7 % [1 9 ]; th re e e m erg e n cy m e d ic in e jo u rn a ls , s tu d ie d ina g g re g a te , 6 9 % [1 8 ]; Jou rna l o f In fe c tious D iseases , 75 %[2 3 ]; a n d New Eng land Jou rna l o f M ed ic ine , 8 9 % [2 0 ].It m u st b e e m ph a s ize d , h o w e ve r, th a t n e ith e r th e fre q u e n tu se o f s ta tis tic a l m e th o d s n o r th e ir d e g re e o f co m p le x ity is sy n-o n ym o u s w ith m a nu s cr ip t q u a lity . E xp e rim e n ta l d e s ig n , c a re fu lm e th o d s , a n d th e u se o f s trin g e n t c r ite r ia to a vo id s u b je c t p re -se le c tio n b ia s a re o fte n m o re im p o rta n t in d e te rm in in g th eo ve ra ll s c ie n tific va lu e o f a p a p e r th a n th e ch o ic e of a p a rtic u la rp o s t h o c s ta tis tica l te s t. E a rly e va lu a tio n s o f M R im a gin g w e recr itic iz e d in th e se re ga rd s [3 6 ]. H o w e ve r, a n a rg u m e n t ca n b em a d e tha t m a n y ra d io lo g y artic le s a re p r im a rily v is u a l o rd e sc rip tive in n a tu re ; th e ir tru e va lu e a n d p o w e r lie in th e re a lmo f a n a to m ic co rre la tio n o r the a ccu ra te a sse s sm e n t o f ra p id lych a n g in g te ch n o lo g y . B y th e ve ry n a tu re o fth e ir s u b je c t m a tte r,th e re fo re , m a n y ra d io lo g y re se a rch p a p e rs d o n o t fo llo w th ep a tte rn o f lo n g -te rm , d o u b le -b lin d e d tr ia ls a p p ro p ria te fo r so m eo th er m ed ica l sp ec ia ltie s.

D es p ite th e se d iffe re n ce s in re se a rc h p h ilo so p h y , th etyp e s o f s ta tis tica l p ro c e d u re s fo u n d in ra d io log ic p u b lica -tio n s a p p e a r s im ila r to th o s e re p o rte d in n o n n a d io lo g ic m ed i-ca l p u b lica tio n s . D e sc rip tive a n a ly s is , s im p le in fe re n ce (t-te s ts ), c o n tin g e n cy ta b le a n a ly s is , a n d b a s ic co n re la tion /re g re ss io n te ch n iq u e s a cco u n t fo r m o s t o f th e s ta tis tic a lte s ts re p o rte d in b o th ra d io lo g ic a n d n o n n a d io lo g ic a rtic le s

[3 0 -3 2 ]. S o m e m e d ic a l p u b lica tio n s n o te d fo r p u b lish in gla rg e -sc a le c lin ica l tr ia ls , s uc h a s th e New Eng land Jou rna lo f M e di cin e on Jou rna l o f the Am e ric an M ed ica l A ssoc ia tion ,us e a d va n ce d e p id e m io lo g ic s ta tis tic s a n d su rv iv a l a n a lys ism u c h m ore e x te n s ive ly th a n Rad io logy o n th e AJR d o [1 0 ,3 2 ]. P a th o lo g y a nd c lin ica l la b o ra to ry jo u rn a ls u se m ath e -m a tica l (p h a rm a co k in e tic ) m o d e lin g a n d n o n lin e a r e s tim a -tio n w ith a p p re c ia b le fre q u e n c y [3 0 ]. C o n ve rse ly , ra d io lo g yjo u rn a ls a p p e a r to u se R O C a n a lys e s a n d o th e r ad v a n ce dd e c is io n s ta tis tics m o re co m m o n ly th a n n o n ra d io lo g ic m e d i-ca l jo u rn a ls d o . N e ve rth e le ss , th e to ta l frac tio n o f th e s ea d va n ce d s ta tis tic a l te c h n iq u e s is so sm a ll in m o st jo u rna lsth a t co n tin u e d re lian c e o n th e b a s ic fo rm s o f s ta tis tica l a n a ly -s is ta u g h t in in tro d u c to ry co u rs e s a n d te x tb o o k s on b io s ta tis -tic s re m a in s a w o rth w h ile e d uc a tio n a l g o a l to im p ro v e th ea b ilitie s o f b o th ra d io lo g is ts a n d n o n ra d io lo g is ts to in te rp re tm e d ica l p u b lica tio n s [3 7 ].

W h a te ve r th e re a s o ns o r p re c ise d is trib u tio n o f s ta tis tica lte s ts m ig h t b e , s ta tis tica l a n a lyse s a re b e c o m in g m o re p ro m i-ne n t in a ll a sp e c ts o f m e dica l jo u rn a lism , in c lu d in g ra d io lo g y .U n fo rtu n a te ly , re ce n t s tu d ie s co n tin u e to s h o w th a t th e a v er-a g e p h ys ic ia n h a s o n ly a p o o r o r su p e rfic ia l k n o w le d g e o f b io -s ta tis tic s a n d g e n e ra lly is p o o rly p re p a re d to c ritica lly e va lu a tem a n y p u b lish e d s tu d ie s [7 -9 ]. It is h o p e d th a t a tte n tio n to th isd iv erg in g in te lle c tu a l g a p w ill e n c o u ra g e p ra c tic in g ra d io lo g is tsto b e co m e m o re fa m ilia r w ith s ta tis tic a l te ch n iq u e s e n co u n -te re d in th e ir p ub li ca ti on s a nd s ti mu la te d ir ec to rs o f r ad io lo gyre s id e n cy p ro g ra m s to b e tte r e d u c a te th e ir tra in e e s in s ta tis ti-ca l m e th o d s a n d e xp e rim e n ta l d e s ig n .

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A JR :16 3 , S ep tem be r 19 93 S T A T IS T IC A L A N A L Y S IS IN AJR A N D RAD IOLOGY 71 5

A C K N O W L E D G M E N TI tha nk D onna G arris on fo r he lp in re sea rch in g b ackg rou nd m ate -

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T h e re a d e rs a tte n tio n is d ire c te d to th e c o m m e n ta ry o n th is a rtic le , w h ic h a p p ea rs o n th e fo llo w in g p a g e s.