EDUCATIONAL AND PSYCHOLOGICAL MEASUREMENT 1970, 30, 607-610. DETERMINING SAMPLE SIZE FOR RESEARCH ACTIVITIES 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 of determining 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 has published a formula for determining sample size. Regrettably a table has not bee available for ready, easy reference which could have been constructed using the following formula. s = X 2 NP (1 − P) ÷ d 2 ( N − 1) + X 2 P(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). 1.96 x 1.96 = 3.8416 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 the sample 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 sample size representative of the teachers in this example is 368. Table 1 is applicable to any defined population. The relationship between sample size and total population is illustrated in Figure 1. It should be noted that as the population increases the sample size increases at a diminishing rate and 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 Table for Determining Sample Size from a Given Population N S 10 10 15 14 20 19 25 24 30 28 35 32 40 36 45 40 50 44 55 48 60 52 65 56 70 59 75 63 80 66 85 70 90 73 95 76 100 80 110 86 120 92 130 97 140 103 150 108 160 113 170 118 180 123 190 127 200 132 210 136 Note.—N is population size. S is sample size. N 220 230 240 250 260 270 280 290 300 320 340 360 380 400 420 440 460 480 500 550 600 650 700 750 800 850 900 950 1000 1100 S 140 144 148 152 155 159 162 165 169 175 181 186 191 196 201 205 210 214 217 226 234 242 248 254 260 265 269 274 278 285 N 1200 1300 1400 1500 1600 1700 1800 1900 2000 2200 2400 2600 2800 3000 3500 4000 4500 5000 6000 7000 8000 9000 10000 15000 20000 30000 40000 50000 75000 1000000 S 291 297 302 306 310 313 317 320 322 327 331 335 338 341 346 351 354 357 361 364 367 368 370 375 377 379 380 381 382 384