SAMPLING IN RESEARCH

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  • #862

    I need an assistance on sampling in research, i have difficulties on selecting samples from a given table of numbers. i just do not have a clue which type of sample can i use. please anyone to help?

    please find an example of a question and try to answer it and give me a hint how did you do it. 

    #866
    Stephen Gorard
    Participant

    Note to all – If you really want a useful answer to a question then the question must be clear. This question and the previous recent one, and many previous, are just about impossible to answer.

     

    Here is my attempt anyway. Always use simple random samping of cases (with replacement) unless it is impossible. If it is impossible your study moves down several notches in quality before it starts.

     

    There are internet tables of random numbers, and random number generators (RAND function in Excel). Put as many digits together as you need to cover the size of the population. Take the numbers in strict order ignoring only those outside the required range.

     

    For example, imagine you had 873 things to pick from (numbers, people, hospitals, sentences,,,,,). You will need three random digits for each case. Imagine you want to pick 10 cases. You will need 30 random digits to start with.

     

    The first 3 digits pick the first case. 3, 4 and 2 lead to case 342 in your ordered list of 873 things. If the next three digits are 9, 8, 6 then 986 is beyond 873, Ignore this set of three, and move to the next three (and you will now need at least 33 random digits). And so on. A perfect sample.

    #865

    thank you Mr Stephen for your attempt. but to be honest i do not understand at all. may be to construct a question relating to what i need to know is very difficulty as a result it is not clear. Mr Stephen can you please attempt to answer the following question for me.

    the SBS School designed a study programme that is considered effective for their 3rd year Students. the total number of 3rd year students in the school is 250. from the total number given only 20 students will be selected to participate in the study programme. the first 10 students will be the experimental group and the second 10 students selected will be the control group. select the 20 students that will participate in the programme from the table of numbers below. start with the number in bold.

    391 311 093 387 323 058 130 372 369 281 186 375 169 256 355 227 348 250 278 097 375 358
    315 081 061 219 371 180 221 194 275 297 400 188 198 264 332 296 139 248 378 157 291 251
    178 398 099 103 092 126 383 335 385 234 324 319 070 095 115 057 230 336 284 174 048 065
    207 044 076 173 244 390 122 395 300 128 283 274 108 341 101 364 392 211 394 111 068 196
    175 333 124 294 240 213 294 051 153 302 216 282 085 049 254 267 132 271 309 365 292 151
    214 217 206 241 041 088 138 348 078 072 184 210 229 171 345 089 399 288 162 179 321 159
    190 287 263 143 237 052 053 242 301 388 223 359 215 382 146 325 147 225 183 310 193 351
    238 313 354 327 047 165 267 321 331 396 200 163 368 381 246 290 062 119 045 265 232 236
    224 259 155 202 252 367 192 187 298 228 247 189 363 203 056 041 277 197 340 273 209 305
    377 257

    i will be delighted that you help me 

    #864
    Stephen Gorard
    Participant

    So that’s easy. Just select 20 random numbers from 1 to 250. 

    If you have Excel, go to a cell. Type “=INT(RAND()*250)+1”. This will give you one number. Copy this cell 19 times. Now you have 20 random numbers. 

    #863

    thanks very much Mr Stephen

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