EDUCATIONAL AND PSYCHOLOGICAL MEASUREMENT_DETERMINING SAMPLE SIZE FOR RESEARCH
1970, 30, 607-610.
DETERMINING SAMPLE SIZE FOR RESEARCH
ACTIVITIES
代写留学生作业ROBERT V. KREJCIE
University of Minnesota, Duluth
DARYLE W. MORGAN
Texas A. & M. University
The ever increasing demand for research has created a need for an efficient method ofdetermining the sample size needed to be representative of a given population. In the article“Small Sample Techniques,” the research division of the National Education Association haspublished a formula for determining sample size. Regrettably a table has not bee available forready, easy reference which could have been constructed using the following formula.
s = X 2NP(1− P) ÷ d 2 (N −1) + X 2P(1− P).
s = required sample size.
X2 = the table value of chi-square for 1 degree of freedom at the desired confidence level
(3.841).
N = the population size.
P = the population proportion (assumed to be .50 since this would provide the maximum
sample size).
d = the degree of accuracy expressed as a proportion (.05).
No calculations are needed to use Table 1. For example, one may wish to know thesample size required to be representative of the opinions of 9000 high school teachers relative to
merit pay increases. To obtain the required sample size enter Table 1 at N = 9000. The samplesize representative of the teachers in this example is 368. Table 1 is applicable to any definedpopulation.
The relationship between sample size and total population is illustrated in Figure 1. Itshould be noted that as the population increases the sample size increases at a diminishing rateand remains relatively constant at slightly more than 380 cases.
REFERENCE
Small-Sample Techniques. The NEA Research Bulletin, Vol. 38 (December, 1960), p. 99.
TABLE 1
T代写留学生作业able for Determining Sample Size from a Given Population
N S N S N S
10 10 220 140 1200 291
15 14 230 144 1300 297
20 19 240 148 1400 302
25 24 250 152 1500 306
30 28 260 155 1600 310
35 32 270 159 1700 313
40 36 280 162 1800 317
45 40 290 165 1900 320
50 44 300 169 2000 322
55 48 320 175 2200 327
60 52 340 181 2400 331
65 56 360 186 2600 335
70 59 380 191 2800 338
75 63 400 196 3000 341
80 66 420 201 3500 346
85 70 440 205 4000 351
90 73 460 210 4500 354
95 76 480 214 5000 357
100 80 500 217 6000 361
110 86 550 226 7000 364
120 92 600 234 8000 367
130 97 650 242 9000 368
140 103 700 248 10000 370
150 108 750 254 15000 375
160 113 800 260 20000 377
170 118 850 265 30000 379
180 123 900 269 40000 380
190 127 950 274 50000 381
200 132 1000 278 75000 382
210 136 1100 285 1000000 384
Note.—N is population size.
S is sample size.