Page 49 - การวิจัยและสถิติทางการศึกษา หน่วยที่ 5

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°“√ÕÕ°·∫∫°“√‡≈◊Õ°°≈ÿà¡µ—«Õ¬à“ß 5-39

°“√°”Àπ¥¢π“¥°≈ÿà¡µ—«Õ¬à“ß„π°√≥’∑’Ë¢π“¥ª√–™“°√∑’Ë°”Àπ¥‰¡àµ√ß°—∫µ—«‡≈¢¢π“¥ª√–™“°√
(N) µ“¡µ“√“ß “¡“√∂°”Àπ¥¢π“¥°≈ÿà¡µ—«Õ¬à“ß‚¥¬„™â¢π“¥°≈ÿà¡µ—«Õ¬à“ß∑’Ë‡À¡“– ¡°—∫ª√–™“°√
¢π“¥„À≠à°«à“∑’ËÕ¬àŸ™—Èπµ‘¥°—π ‡™àπ „π°“√«‘®—¬°“√»÷°…“ªí≠À“·≈–§«“¡µâÕß°“√„π°“√‡√’¬πµàÕ¢Õßπ—°‡√’¬π
™—Èπ¡—∏¬¡»÷°…“ªï∑’Ë 6 ∑’Ë¡’ª√–™“°√ 5,500 §π ¢π“¥°≈ÿà¡µ—«Õ¬à“ß∑’Ë§«√„™â§◊Õ 361 §π ‡ªìπµâπ À√◊ÕÕ“®
„™â«‘∏’°“√‡∑’¬∫∫—≠≠—µ‘‰µ√¬“ß§å ¥—ßπ’È

∂â“ª√–™“°√ 5,000 §π ¢π“¥µ—«Õ¬à“ßµ“¡µ“√“ß„™â 357 §π ·≈–∂â“ª√–™“°√ 6,000 §π
¢π“¥µ—«Õ¬à“ßµ“¡µ“√“ß„™â 361 §π ®–‡ÀÁπ«à“

ª√–™“°√µà“ß°—π (6,000 › 5,000) 1,000 §π ¢π“¥µ—«Õ¬à“ßµà“ß°—π (361 › 357) 4 §π
500

ª√–™“°√µà“ß°—π (5,500 › 5,000) 500 §π ¢π“¥µ—«Õ¬à“ßµà“ß°—π ✕ 4 = 2 §π
1,000

¥—ßπ—Èπ °√≥’ª√–™“°√ 5,500 §π §«√„™âµ—«Õ¬à“ßÕ¬à“ßπâÕ¬ 359 §π

3. °“√°”Àπ¥¢π“¥µ—«Õ¬à“ß‚¥¬„™âµ“√“ß ”‡√Á®√Ÿª¢Õß´“·≈π·≈–¥‘≈·¡π (Salant and
Dillman) ´“·≈π·≈–¥‘ ·¡π‰¥â®—¥∑”µ“√“ß ”‡√Á®√Ÿª‡æ◊ËÕ„™â°”Àπ¥¢π“¥°≈àÿ¡µ—«Õ¬à“ß ‚¥¬æ‘®“√≥“®“°
®”π«πª√–™“°√ §ÿ≥≈—°…≥–¢Õßª√–™“°√ (charadeteristics) ·≈–§«“¡·¡àπ¬” (precision) ∑’Ë√–¥—∫
§«“¡‡™◊ËÕ¡—Ëπ 95 ‡ªÕ√å‡´Áπµå

µ“√“ß∑Ë’ 5.6 µ“√“ß°”Àπ¥¢π“¥µ—«Õ¬à“ß¢Õß´“·≈π·≈–¥‘≈·¡π

¢π“¥ §«“¡§≈“¥‡§≈Õ◊Ë π„π°“√ ÿ¡à °≈à¡ÿ µ—«Õ¬à“ß
ª√–™“°√ ±3% ±5% ±10%

§≥ÿ ≈°— …≥–¢Õßª√–™“°√

50/50 80/20 50/50 80/20 50/50 80/20

100 92 87 80 71 49 38
250 203 183 152 124 70 49
500 341 289 217 165 81 55
750 441 358 254 185 85 57
1,000 516 406 278 198 88 58
2,500 748 537 333 224 93 60
5,000 880 601 357 234 94 61
10,000 964 639 370 240 95 61
25,000 1,023 665 378 234 96 61
50,000 1,045 674 381 245 96 61
100,000 1,056 678 383 245 96 61
1,000,000 1,066 682 384 246 96 61
100,000,000 1,067 683 384 246 96 61

∑¡Ë’ “: Salant, Priscillan and Dillman, Don A. How to Conduct Your Own Survey. 1994, p. 55.

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