Page 178 - สถิติทางวิทยาศาสตร์สุขภาพ เพื่อการวิจัย

2 2
¢âÕ§«√√–«—ß „π°“√§”π«≥¢π“¥µ—«Õ¬à“ß s °”Àπ¥¡“®“°§à“ s ®“°√“¬ß“π«‘®—¬∑’Ë
d d
2
ºà“π¡“§à“ s §”π«≥®“°°“√π”§à“¢Õß·µà≈–§Ÿà¡“À“º≈µà“ß π”§à“º≈µà“ß∑’ˉ¥â¡“§”π«≥§à“‡©≈’ˬ
d
2
·≈–§«“¡·ª√ª√«π ‰¡à„™à§à“§«“¡·ª√ª√«π (s ) ¢Õß°≈ÿà¡„¥°≈ÿà¡Àπ÷Ëß °“√π”§à“§«“¡·ª√ª√«π
2 2
®“°√“¬ß“π«‘®—¬¡“„™â„π°“√§”π«≥¢π“¥µ—«Õ¬à“ßµâÕßµ√«® Õ∫„Àâ·πà„®«à“‡ªìπ s ‰¡à„™à s ‡æ√“–
d
∑—Èß 2 µ—«¡’§à“·µ°µà“ß°—π
2 2
„π√“¬ß“π«‘®—¬∑’ˉ¡à‰¥â„Àâ§à“ s ·µà„Àâ§à“ t (dependent t) π—°«‘®—¬ “¡“√∂§”π«≥§à“ s
d d
2
‰¥â®“° s = d n/t ∂Ⓣ¡à„Àâ§à“ d „À⧔π«≥®“° x - x
d 1 2

10.3 °“√§”π«≥¢π“¥µ—«Õ¬à“߇æ◊ËÕ°“√‡ª√’¬∫‡∑’¬∫ —¥ à«π
√–À«à“ߪ√–™“°√ 2 °≈ÿà¡∑’˵—«Õ¬à“ß„π·µà≈–°≈ÿࡉ¡à‡ªìπÕ‘ √–µàÕ°—π

·∫∫ß“π«‘®—¬∑’Ë¡’°“√„Àâ ‘Ëß∑¥≈Õß„πÀπ૬»÷°…“‡¥’¬«°—π 2 Õ¬à“ß ‡™àπ °“√∑¥ Õ∫§«“¡√Ÿâ

°àÕπ-À≈—ß°“√»÷°…“ (before-after study) À√◊Õ¡’‡ß◊ËÕπ‰¢®—∫§ŸàÀπ૬»÷°…“√–À«à“ß°≈ÿࡵ—«Õ¬à“ß
·≈–¡’µ—«·ª√∑’Ë„™âµÕ∫§”∂“¡À≈—°‡ªìπµ—«·ª√∑’ˇªìπ¢âÕ¡Ÿ≈°≈ÿà¡∑’Ë √ÿªº≈„π√Ÿª¢Õß —¥ à«π Ÿµ√∑’Ë„™â„π°“√
§”π«≥¢π“¥µ—«Õ¬à“ߢÕß Connett et al §◊Õ

È 2 ˘ 2
Í b + b + 1Â - b ˙
Í Z a c + 1 Z b Ä c pÄ c - 1Â ˙
n= Î ˚
b 2
pÄ - 1Â
c

‚¥¬∑’Ë n= ¢π“¥µ—«Õ¬à“ß

b ·≈– c = ®”π«πÀπ૬ —߇°µ„π™àÕß b ·≈– c
b c
p= À√◊Õ ∑’Ë¡’§à“‡≈Á° (§à“ b, c ·≈– n π”¡“®“°√“¬ß“π«‘®—¬∑’˺à“π¡“)
n n

10.3 °“√§”π«≥¢π“¥µ—«Õ¬à“߇æ◊ËÕ°“√‡ª√’¬∫‡∑’¬∫ —¥ à«π√–À«à“ߪ√–™“°√ 2 °≈ÿà¡œ 177

∫∑∑’Ë10 177 31/7/09, 5:17 PM