Page 1

º··Õ5è ¡ÒÃÊØ‹ÁµÑÇÍ‹ҧ


1. ¡ÒÃÊØÁ‹ µÑÇÍ‹ҧâ´ÂäÁ‹ãªŒ¤ÇÒÁ¹‹Ò¨Ð໚¹ (Non Probability Random Sampling)

 ¡ÒÃàÅ×Í¡â´ÂºÑ§àÍÔÞ  ¡ÒÃàÅ×Í¡â´Â੾ÒÐà¨ÒШ§  ¡ÒÃàÅ×Í¡µÒÁâ¤ÇµŒÒ  ÁÕ¤ÇÒÁÅíÒàÍÕ§  à¾ÃÒТŒÍÁÙÅᵋÅФ‹ÒËÃ×ÍᵋÅÐ˹‹ÇÂäÁ‹ ÁÕâÍ¡Òʶ١àÅ×Í¡ä´Œà·‹Ò æ ¡Ñ¹ «Ö§è ·íÒãËŒ¡ÒûÃÐÁÒ³¤‹Òä»Âѧ »ÃЪҡÃäÁ‹¶¡Ù µŒÍ§


1. ¡ÒÃÊØÁ‹ µÑÇÍ‹ҧâ´ÂäÁ‹ãªŒ¤ÇÒÁ¹‹Ò¨Ð໚¹  ¡ÒÃàÅ×Í¡µÑÇÍ‹ҧẺºÑ§àÍÔÞ (Accidental Sampling) • àÅ×Í¡µÒÁ¤ÇÒÁÊдǡ ºÑ§àÍÔÞà´Ô¹¼‹Ò¹ÁÒ ¼Ù·Œ àÕè ¢ŒÒªÁʶҹ·Õè ¤ÇÒÁ¾Ö§¾Íã¨ã¹¡ÒÃ㪌ºÃÔ¡Òø¹Ò¤ÒÃ

¨ÐÁÕ¤ÇÒÁà͹àÍÕ§ÁÒ¡àÁ×Íè ¹íÒä»ÊÃػ͌ҧÍÔ§¶Ö§»ÃЪҡÃ


2. ¡ÒÃÊØÁ‹ µÑÇÍ‹ҧâ´ÂäÁ‹ãªŒ¤ÇÒÁ¹‹Ò¨Ð໚¹  ¡ÒÃàÅ×Í¡µÑÇÍ‹ҧẺà¨ÒШ§ºÑ§àÍÔÞ (Purposive Sampling) • à¨ÒШ§¡ÅØÁ‹ µÑÇÍ‹ҧ • àËÁÒСѺ¡ÒÃÇÔ¨ÂÑ á¹ÇÅÖ¡ ·ÕèµÍŒ §ÍÒÈѤÇÒÁÃÙŒ ¤ÇÒÁ ªíÒ¹ÒÞ੾ÒÐà¡ÕÂè ǡѺ»ÃЪҡà  à¾×Íè ŴͤµÔáÅÐ

¤ÇÒÁÅíÒàÍÕ§㹡ÒÃà¡çº¢ŒÍÁÙÅ


2. ¡ÒÃÊØÁ‹ µÑÇÍ‹ҧâ´ÂäÁ‹ãªŒ¤ÇÒÁ¹‹Ò¨Ð໚¹

 ¡ÒÃàÅ×Í¡µÑÇÍ‹ҧẺâ¤ÇµŒÒ (Quota Sampling) • ¡íÒ˹´ÊѴʋǹ¢Í§»ÃЪҡÃäÇŒÅÇ‹ §Ë¹ŒÒ • ¡íÒ˹´¤Ø³ÊÁºÑµºÔ Ò§»ÃСÒà  ÈÖ¡ÉÒ¡ÒÃ㪌ËÍŒ §ÊÁØ´¢Í§¹È.ªÒÂáÅÐËÞÔ§ Á·Ã.Ōҹ¹Ò

¨íҹǹ¹È.ªÒÂáÅйÈ.ËÞÔ§ ෋ҡѹ ËÃ×͵ÒÁÊѴʋǹ¢Í§»ÃЪҡÃ

 ¡ÒÃÃѺÊÁѤùѡÈÖ¡ÉÒÃͺâ¤ÇµŒÒ (17 ¨Ñ§ËÇÑ´ÀÒ¤à˹×Í) à¾×Íè ࢌÒÈÖ¡ÉÒÁ·Ã. Ōҹ¹Ò ÀÒ¤¾ÒÂѾ

 à¡Ã´à©ÅÕÂè


2. ¡ÒÃÊØÁ‹ µÑÇÍ‹ҧâ´Â㪌¤ÇÒÁ¹‹Ò¨Ð໚¹ (Probability Random Sampling)

¡ÒÃÊØ‹ÁµÑÇÍ‹ҧÍ‹ҧ§‹Ò ◦ ¡ÒÃÊØ‹ÁµÑÇÍ‹ҧẺÁÕÃкº ◦ ¡ÒÃÊØ‹ÁµÑÇÍ‹ҧẺÁÕª¹ Ñé ÀÙÁÔ ◦ ¡ÒÃÊØ‹ÁµÑÇÍ‹ҧẺ¡ÅØÁ ‹ ◦

 ໚¹¡ÒÃÊØ‹ÁµÑÇÍ‹ҧ·ÕèÁ¤Õ ÇÒÁÂص¸Ô ÃÃÁ ໚¹¡ÒÃÊØ‹ÁµÑÇÍ‹ҧ·Õ´è Õ 

à¾ÃÒТŒÍÁÙÅᵋÅФ‹ÒËÃ×ÍᵋÅÐ˹‹ÇÂÁÕâÍ¡Òʶ١àÅ×Í¡ä´Œà·‹Ò æ ¡Ñ¹


◦ »ÃЪҡÃÁÕâÍ¡Òʶ١àÅ×Í¡à·‹Ò æ ¡Ñ¹ ◦ ᵋÅлÃÐªÒ¡Ã·Õ¶è ¡Ù àÅ×͡໚¹ÍÔÊÃе‹Í¡Ñ¹äÁ‹à¡ÕÂè Ǿѹ¡Ñ¹ ◦ »ÃÐªÒ¡Ã¹Ñ¹é ¤ÇÃÁÕÅѡɳФŌÒ¤ÅÖ§¡Ñ¹ (Homogeneity) äÁ‹

ᵡµ‹Ò§¡Ñ¹ÁÒ¡¹Ñ¡

ÁÕ 2 ÇÔ¸Õ

1. Ẻ¨Ñº©ÅÒ¡ (Lottery) 2. Ẻ㪌µÒÃÒ§àÅ¢ÊØ‹Á (Random

Number Table)


 Ẻ¨Ñº©ÅÒ¡ (Lottery) ઋ¹ µŒÍ§¡ÒäѴàÅ×Í¡¹Ñ¡ÈÖ¡ÉÒ 3 ¤¹ ¨Ò¡»ÃЪҡùѡÈÖ¡ÉÒ ¤¹ ÍÍ¡ÁÒ·íÒẺ½ƒ¡ËѴ˹ŒÒˌͧàÃÕ¹

30

◦ ÇÔ¸Õ¡ÒÃÊØ‹Á ◦ à¢Õ¹ª×Íè ŧ㹺ѵà 30 Ἃ¹ ◦ ◦

¨ÑººÑµÃ¢Ö¹é ¤ÃÑé§ÅÐ 1 Ἃ¹

¨´ºÑ¹·Ö¡äÇŒáŌǹíҺѵÃãÊ‹¤¹× ãËŒÁÕ 30 Ἃ¹àÊÁÍ (à¾×Íè ãËŒâÍ¡ÒÊ 1 ä´ŒÃºÑ àÅ×͡໚¹ 30 àÊÁÍ


 Ẻ㪌µÒÃÒ§àÅ¢ÊØÁ‹ (Random Number Table) ◦ ÇÔ¸¡Õ ÒÃÊØÁ‹

¡íÒ˹´ËÁÒÂàÅ¢ãËŒ¡Ñº·Ø¡¤‹Ò¢Í§»ÃЪҡà àÅ×Í¡àÅ¢µÑÇááÍ‹ҧÊØ‹Áã¹µÒÃÒ§àÅ¢ÊØ‹Á  ªÕéä»·ÕèàÅ¢ã´àÅ¢ ˹Öè§â´ÂäÁ‹à¨ÒШ§ ◦ Í‹Ò¹µÑÇàÅ¢ ¨Ò¡¢ÇÒ仫ŒÒ ËÃ×Í ¨Ò¡«ŒÒÂ仢ÇÒ ËÃ×Í ¨Ò¡¢ŒÒ§º¹Å§¢ŒÒ§Å‹Ò§ ËÃ×Í Í‹Ò¹µÒÁá¹Ç·á§ ◦ àÅ×͡㪌àÅ¢¡ÕèËÅÑ¡  ¨íҹǹ»ÃЪҡà • ¶ŒÒ¨íҹǹ»ÃЪҡÃÁÕ 2 ËÅÑ¡ ¡çÍ‹Ò¹àÅ¢ 2 µÑÇ • ¶ŒÒÁÕ 3 ËÅÑ¡ ¡çÍ‹Ò¹ 3 µÑÇ ◦ ◦


 Ẻ㪌µÒÃÒ§àÅ¢ÊØ‹Á (Random

Number Table)

ÁÕ»ÃЪҡà 50 ¨íҹǹ áÅÐ µŒÍ§¡ÒõÑÇÍ‹ҧ 5 ¨íҹǹ

ÇÔ¸¡Õ ÒÃÊØÁ‹  ãËŒËÁÒÂàÅ¢»ÃЪҡà µÑé§áµ‹ 00, 01, 02, 03, ... , 49

( 2 ËÅÑ¡)

 ÊØ‹ÁµÑÇàÅ¢µÑÇ˹Ö觨ҡµÒÃÒ§àÅ¢ÊØ‹Á ÊÁÁµÔä´ŒàÅ¢ 4 ¨Ò¡ 10480


 Ẻ㪌µÒÃÒ§àÅ¢ÊØÁ‹ (Random Number Table)

ÊØ‹Á 2 ËÅÑ¡  àÅ×Í¡àÅ¢ 2 µÑÇ  àÅ×Í¡¨Ò¡ «ŒÒÂ仢ÇÒ

จะได้

48 01 50 11 01 53 60 20 11 81 …

¾Ô¨ÒóҵÑÇàÅ¢·Õàè »š¹ä»ä´ŒáÅÐäÁ‹«éíÒ ãËŒ¤Ãº 5 µÑÇ จะได้

48 01 11 20 16


◦ 㪌¡º Ñ »ÃЪҡ÷ÕÁè ¡Õ ÒèѴàÃÕ§änj໚¹ÃкºáÅŒÇ ◦ ᵋÅФ‹Ò¢Í§»ÃЪҡà 䴌¶¡Ù àÃÕ§໚¹áººÊØÁ‹ ÍÂÙá ‹ ÅŒÇ ◦ ໚¹¡ÒÃàÅ×͡໚¹ª‹Ç§ æ  ·Ø¡ æ k ˹‹Ç ¨Ð¶Ù¡àÅ×Í¡ â´Â·Õè

N k= n N – จํ านวนประชากร n – จํ านวนตัวอย่าง


◦ ઋ¹

N = 50

áÅÐ n = 5

5 0 k= = 10 5 ◦ ¨Ò¡µÒÃÒ§àÅ¢ÊØÁ‹  àÅ×Í¡µÑÇàÅ¢ÊØÁ‹ 2 ËÅÑ¡·ÕÁè ¤Õ ‹Ò¹ŒÍÂ

¡Ç‹ÒËÃ×Í෋ҡѺ 10 ÁÒË¹Ö§è µÑÇ (00, 01, 02, … , 09)  ÊÁÁµÔä´ŒàÅ¢ 05

◦ àÅ×Í¡µÑÇÍ‹ҧ·Õè

05, 15, 25, … , 45


◦ ÍÒ¨·íÒãËŒà¡Ô´¤ÇÒÁÅíÒàÍÕ§ ઋ¹ ¡ÒÃÊØÁ‹ ¤Ðá¹¹

¹Ñ¡ÈÖ¡ÉÒàÁ×Íè ¹Ñ¡ÈÖ¡ÉÒä´Œ¶¡Ù àÃÕ§µÒÁÅíҴѺ¤Ðá¹¹

◦ 㹡óշÕè n ËÒà N äÁ‹Å§µÑÇ ¨ÐãËŒ k ໚¹¨íҹǹ

àµçÁ·Õãè ¡ÅŒà¤Õ§¡ÑN º n

ÁÒ¡·ÕèÊ´Ø


 㪌¡º Ñ »ÃЪҡ÷ÕÁè ¤Õ ÇÒÁᵡµ‹Ò§¡Ñ¹ÁÒ¡

ËÅÑ¡¡ÒÃÊØÁ‹ µÑÇÍ‹ҧ  µŒÍ§áº‹§»ÃЪҡÃÍ͡໚¹ªÑ¹é ËÃ×;ǡ (Stratum)  ÍҨẋ§â´Â㪌µÇÑ á»Ã¨íÒṡ (Classification Variable) ઋ¹

à¾È ÍÒªÕ¾ ÈÒÊ¹Ò ¡ÒÃÈÖ¡ÉÒ ÃдѺªÑ¹é ໚¹µŒ¹  ᵋÅЪѹé  ÁÕ¤ÇÒÁᵡµ‹Ò§·ÕÊè ´Ø áÅÐ

ÀÒÂ㹪ѹé à´ÕÂǡѹ  ÁÕ¤ÇÒÁ ¤ÅŒÒ¤ÅÖ§¡Ñ¹ÁÒ¡·ÕèÊ´Ø


µÑÇÍ‹ҧ »ÃЪҡùѡÈÖ¡ÉÒ 200 ¤¹ µŒÍ§¡ÒõÑÇÍ‹ҧ

50 ¤¹

 㪌 “à¾È” ໚¹µÑÇá»Ã¨íÒṡ

ËÞÔ§ 120 ¤¹  ËÒ¨íҹǹµÑÇÍ‹ҧ·Õ¨è ÐÊØÁ‹ - 80 ªÒ , ËÞÔ §   = ×5 0 = 20 คน   ¨íҹǹµÑÇÍ‹ҧ¹.È.ªÒ  200 2 0 1  = 0 = 30 คน  ×5 ¨íҹǹµÑÇÍ‹ҧ¹.È.ËÞÔ§ 00 2  ªÒÂ

80 ¤¹


แยกออกเป็ น stratum สุ่มตัวอย่างตามสัดส่วน


 ¡ÃͺËÃ×͢ͺࢵ¢Í§µÑÇÍ‹ҧ ËÒä´ŒÂÒ¡

ËÅÑ¡¡ÒÃÊØÁ‹ µÑÇÍ‹ҧ  ẋ§»ÃЪҡÃÍ͡໚¹¡ÅØ‹Á (Cluster)  ¢¹Ò´¢Í§áµ‹ÅСÅØ‹Á෋ҡѹ ËÃ×͵‹Ò§¡Ñ¹¡çä´Œ  ¡ÒÃàÅ×Í¡µÑÇÍ‹ҧ¨ÐàÅ×Í¡ÁÒà¾Õ§ºÒ§¡ÅØ‹Á  ઋ¹ ẋ§Í͡໚¹ ÀÒ¤ , ¨Ñ§ËÇÑ´ , ÍíÒàÀÍ , µíҺŠ,ËÁÙº ‹ ÒŒ ¹

ÀÒÂ㹡ÅØÁ‹ à´ÕÂǡѹ  ÁÕ¤ÇÒÁᵡµ‹Ò§ÁÒ¡·ÕÊè ´Ø áµ‹ÅСÅØÁ‹  ÁÕ¤ÇÒÁ ¤ÅŒÒ¤ÅÖ§¡Ñ¹ÁÒ¡·ÕÊè ´Ø

áÅÐ


µÑÇÍ‹ҧ µíÒºÅ˹Öè§ÁÕ 5 ËÁÙ‹ºŒÒ¹ µŒÍ§¡ÒÃÊØ‹Á¤¹ 50 ¤¹  ᵋÅÐËÁÙ‹ºŒÒ¹¡ç¤×Í áµ‹ÅСÅØ‹Á (ÀÒÂ㹡ÅØ‹Áᵡµ‹Ò§¡Ñ¹, ᵋÅСÅØ‹Á¤ÅŒÒ¤ÅÖ§¡Ñ¹)  ÊØ‹ÁËÁÙ‹ºŒÒ¹ÁÒ¡‹Í¹  ÊØ‹Á¤¹¨Ò¡ËÁÙ‹ºŒÒ¹·ÕèÊØ‹Áä´Œ ´ŒÇ¡ÒÃÊØ‹ÁµÑÇÍ‹ҧẺ§‹ÒÂ

 ¡ÒÃÊØ‹ÁẺ§‹ÒÂÊдǡáÅлÃÐËÂÑ´ ᵋ¨ÐÁÕ¤ÇÒÁ

¤ÅÒ´à¤Å×è͹㹡ÒÃÊØ‹ÁµÑÇÍ‹ҧ (Sampling Error) ÊÙ§


แยกออกเป็ น cluster

สุ่มตัวอย่างตามสัดส่วน


1. ¶ŒÒäÁ‹·ÃÒº¢¹Ò´¢Í§»ÃЪҡà ᵋ·ÃÒº¤ÇÒÁá»Ã»Ãǹ¢Í§ »ÃЪҡà 2 Z ⋅σ 2

n=

àÁ×èÍ Z e σ2

α /2

2 e n ¤×Í ¨íҹǹµÑÇÍ‹ҧ ¤×Í ÃдѺ¤ÇÒÁÁѹè 㨷աè Òí ˹´¢Ö¹é ¤×Í ¤ÇÒÁ¤ÅÒ´à¤Å×Íè ¹·Õ¨è ÐÂÍÁÃѺ䴌 (%) ¤×Í ¤ÇÒÁá»Ã»Ãǹ¢Í§»ÃЪҡÃ


2. ¶ŒÒäÁ‹·ÃÒº¢¹Ò´¢Í§»ÃЪҡà ᵋ·ÃÒº¤ÇÒÁá»Ã»Ãǹ¢Í§ »ÃЪҡà 2 Z α /2⋅ pq n= 2 e

àÁ×èÍ

Z e p q

n ¤×Í ¤×Í ¤×Í =

¤×Í ¨íҹǹµÑÇÍ‹ҧ ÃдѺ¤ÇÒÁÁѹè 㨷աè Òí ˹´¢Ö¹é ¤ÇÒÁ¤ÅÒ´à¤Å×Íè ¹·Õ¨è ÐÂÍÁÃѺ䴌 (%) ÊѴʋǹ¢Í§»ÃЪҡ÷յè ÍŒ §¡Òà 1-p


3. ¶ŒÒäÁ‹·ÃÒº¢¹Ò´¢Í§»ÃЪҡà áÅÐäÁ‹·ÃÒº·Ñ§é ¤ÇÒÁ á»Ã»Ãǹ¢Í§»ÃЪҡÃáÅÐÊѴʋǹ¢Í§»ÃÒ÷յè ÍŒ §¡Òà n=

àÁ×èÍ

Z e

2 Z

α /2

4e2

n ¤×Í ¨íҹǹµÑÇÍ‹ҧ ¤×Í ÃдѺ¤ÇÒÁÁѹè 㨷աè Òí ˹´¢Ö¹é ¤×Í ¤ÇÒÁ¤ÅÒ´à¤Å×Íè ¹·Õ¨è ÐÂÍÁÃѺ䴌 (%)


4. ÊٵâͧÂÒÁÒà¹

(Yamane)

 㪌¡º Ñ ¢ŒÍÁÙÅÍѹµÃÀÒ¤ áÅТŒÍÁÙÅÍѵÃÒʋǹ (¢ŒÍÁÙŵ‹Íà¹×èͧ)  µŒÍ§»ÃÐÁÒ³ ¢¹Ò´»ÃЪҡÃ

áÅÐ ¤ÇÒÁ¤ÅÒ´à¤Å×è͹ ¡‹Í¹

 ¤ÇÒÁ¤ÅÒ´à¤Å×Íè ¹¢Ö¹é ÍÂÙ¡‹ Ѻ¤ÇÒÁàª×Íè ¢Í§¼ÙÈŒ ¡Ö ÉÒ/ÇÔ¨ÑÂ

 ໚¹à¾Õ§á¹Ç·Ò§ã¹¡ÒäíҹdzËÒ¢¹Ò´¢Í§µÑÇÍ‹ҧ  ³ ÃдѺ¤ÇÒÁàª×Íè ÁÑ¹è ·Õè 95% áÅÐ 99%


 ¢¹Ò´¢Í§¡ÅØ‹ÁµÑÇÍ‹ҧ·ÕÃè дѺ¤ÇÒÁàª×Íè Áѹè

n=

95%

N 1+Ne2

n - µÑÇÍ‹ҧ N - »ÃЪҡà e - ¤ÇÒÁ¤ÅÒ´à¤Å×Íè ¹·ÕÂè ÍÁÃѺ䴌

(%)


 ¢¹Ò´¢Í§¡ÅØ‹ÁµÑÇÍ‹ҧ·ÕÃè дѺ¤ÇÒÁàª×Íè Áѹè

n=

99%

2.25N 2.25+Ne2

n - µÑÇÍ‹ҧ N - »ÃЪҡà e - ¤ÇÒÁ¤ÅÒ´à¤Å×Íè ¹·ÕÂè ÍÁÃѺ䴌

(%)


âç§Ò¹¼ÅÔµ¡ÃШ¡áË‹§Ë¹Ö§è µŒÍ§¡ÒûÃÐÁÒ³¤ÇÒÁ˹Ңͧ¡ÃШ¡ σ= â´Âà©ÅÕè«֧è ä´ŒÃºÑ ÁÒ¨Ò¡âç§Ò¹Í×¹è â´ÂʋǹàºÕeè§ູÁҵðҹ¢Í§¤ÇÒÁ = 12 ˹Ңͧ¡ÃШ¡ÁÕ¤Ò‹ 12 ÁÔÅÅÔàÁµÃ ¨§ËÒNjҨеŒÍ§ãªŒ 3 µÇÑ Í‹ҧ¨íҹǹ à·‹Òã´ÁÒ·´Êͺ ·Õ¨è ÐãËŒ¤ÇÒÁ¼Ô´¾ÅÒ´ÁÕÍ‹ҧÁÒ¡à¾Õ§ 3 ÁÔÅÅÔàÁµÃ ´ŒÇÂÃдѺ¤ÇÒÁàª×Íè ÁÑè¹ 90% P= 

0.9 p/2 = 0.45

หา Z

P=0.9 Z1 0

Z2 Z0.05 = ?

¨Ò¡µÒÃÒ§

Z0.05 = 1.645


σ=

¨Ò¡

12 e = 3

Z

0.05

= 1.645

äÁ‹·ÃÒº¢¹Ò´»ÃЪҡà ᵋ·ÃÒº σ 2 2 n= =

Z α /2⋅σ

e2

1.6452× 122

32

= 43.30 ≈ 44 ¨ÐµŒÍ§ãªŒµÑÇÍ‹ҧ¨íҹǹÍ‹ҧ¹ŒÍ 44 µÑÇÍ‹ҧ ´ŒÇ¤ÇÒÁàª×Íè ÁÑè¹ 90%


 ¼ÙŒ¨Ñ´¡Òý†Ò¡ÒüÅÔ p = µµŒÍ§¡ÒäǺ¤ØÁ¤Ø³ÀÒ¾ÊÔ¹¤ŒÒ¡‹Í¹·Õè¨ÐÊ‹§Áͺ ãËŒªÒÇÅÙ¡¤ŒÒµ‹Ò§»ÃÐà·È ¨ÐµŒÍ§ãªŒµÑÇÍ‹ҧ෋Òã´ ËÒ¡¡íÒ˹´ãËŒÊѴʋǹ 0.4 ¢Í§»ÃÐªÒ¡Ã·Õ e èµ=ŒÍ§¡ÒèÐÊØ‹Á¤×Í 40% «Ö觨еŒÍ§àÅ×Í¡ÊÔ¹¤ŒÒ¹ÕéÁÒ·´Êͺ Ç‹ÒÁդسÀÒ¾µÒÁ·Õ 0.05 èÂÍÁÃѺ䴌ËÃ×ÍäÁ‹ â´ÂÂÍÁãËŒÁբͧàÊÕÂËÃ×ÍÊÔ¹¤ŒÒ´ŒÇ P= ¤Ø³ÀҾ䴌 5% ·ÕèÃдѺ¤ÇÒÁàª×èÍÁÑè¹ 95%

ËÒ Z P=0.95 Z1 0

0.95 p/2 = 0.475 ¨Ò¡µÒÃÒ§

Z2 Z0.025 = ?

Z0.025 = 1.96


p=

0.4 จาก

q=

0.6

1-0.4 = e =

0.05

äÁ‹·ÃÒº¢¹Ò´»ÃЪҡà áÅÐäÁ‹·ÃÒº σ

Z

0.025

1.96

=

2

n =

=

Z α /2⋅ pq

e2

1.962× 0.4× 0.6

0.052

= 368.79≈ 369 ¨ÐµŒÍ§ãªŒµÑÇÍ‹ҧÊÔ¹¤ŒÒÁÒ·´ÊͺÍ‹ҧ¹ŒÍ 369 ªÔé¹ ´ŒÇ¤ÇÒÁàª×Íè Áѹè 95%


 ÊÁÁµÔÇÒ‹ ÃÑ°ºÒŵŒÍ§¡ÒûÃÐÁÒ³¤‹ÒÊѴʋǹ¢Í§¤Ãͺ¤ÃÑÇã¹ËÁÙº‹ ŒÒ¹ µÑÇÍ‹ҧáË‹e§Ë¹Ö=§è ·Õ迧˜ ÃÒ¡ÒÃÇÔ·ÂØáË‹§»ÃÐà·Èä·Â໚¹»ÃШíÒ ÍÂÒ¡ ·ÃҺNjҨеŒÍ0.1 §ãªŒµÑÇÍ‹ҧ¢¹Ò´à·‹Òã´ ¨Ö§¨Ð·íÒãËŒ¤ÇÒÁ¤ÅÒ´à¤Å×Íè ¹ã¹ ¡ÒûÃÐÁÒ³¹ŒÍÂ¡Ç‹Ò 10% â´Â㪌ÃдѺ¤ÇÒÁàª×Íè Áѹè P99% =

หา Z P=0.99 Z1 0

0.99 p/2 = 0.495 ¨Ò¡µÒÃÒ§

Z2 Z0.005 = ?

Z0.005 = 2.576


Z

e = 0.1

0.005

2.576

=

äÁ‹·ÃÒº¢¹Ò´»ÃЪҡà äÁ‹·ÃÒº σ áÅÐäÁ‹·ÃÒºÊѴʋǹ¢Í§»ÃЪҡÃ

¨Ò¡

2

n

=

=

Z α /2

4e2

2.5762

4(0.1)2 = 165.89≈ 166

¨ÐµŒÍ§ãªŒµÑÇÍ‹ҧ¤Ãͺ¤ÃÑÇÍ‹ҧ¹ŒÍ 166 ¤Ãͺ¤ÃÑÇ ´ŒÇ¤ÇÒÁàª×Íè Áѹè 99%


N= 1,000  ¶ŒÒ¢¹Ò´¢Í§»ÃЪҡÃÁÕ¨íҹǹ 1,000 ˹‹Ç ¨§ËÒ ¢¹Ò´¢Í§µÑÇÍ‹ҧ·ÕèÃдѺ¤ÇÒÁàª×èÍÁÑè¹ 95% áÅÐ 99% â´Â e= ÁÕ¤ÇÒÁ¤ÅÒ´à¤Å×è͹·Õè¨ÐÂÍÁÃѺ䴌෋ҡѺ 5% 0.05 ¢¹Ò´¢Í§µÑÇÍ‹ҧ·ÕÃè дѺ¤ÇÒÁàª×èÍÁѹè 95 % N ¨Ò¡ n = 1+Ne2 1,000 = 285.71 ≈ 286 ¤¹ n= 1+(1,000× 0.052)


N = 1000

e = 0.05

¢¹Ò´¢Í§µÑÇÍ‹ҧ·ÕÃè дѺ¤ÇÒÁàª×èÍÁѹè 99 % ¨Ò¡

n= =

2.25N 225+Ne2

2.25(1,000) 2.25+(1,000× 0.052)

= 473.68 ≈ 474 ¤¹

บทที่ 5 การสุ่มตัวอย่าง