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PROCEDURE FOR SELECTING RANDOM LOCATIONS FOR SAMPLING

By Doug Johnson, Extension Entomologist

University of Kentucky College of Agriculture


These figures are designed to help you remove your personal bias while selecting sampling points in a field. You will have to modify them to fit larger and smaller fields.


  1. Divide the field into general sampling areas.

  2. Randomly select one number between 1 and 100 for each general sampling area.

  3. Consult Table 2. 100 Sets of Random Site Selection Directions, under ENTRY NUMBER, to find the random numbers you have selected. Record the set of walking instructions listed in the table for each of your random numbers.

  4. Select the first area of the field to be scouted.

  5. Go to the edge of that area. If this is a field edge go 30 paces into the field. This is your starting point.

  6. Use the walking instructions to locate your actual sample site.

  7. Take your sample.


As an example: let's look at a small corn field of 20 acres. According to the University of Kentucky IPM Scout Manual a field this size requires 3 samples to be taken.

  1. Divide the field into three general sampling areas.

  2. Select three random numbers say, 2, 31, 24.

  3. Look at Table 2 for Entry Numbers 2, 31, and 24 and you will find the following walking instructions:

    Example Site Selection
    General Sampling AreaEntry NumberDirection - Left or RightPaces - Left or RightPaces Away
    12Right319
    231Right315
    324Left91

  4. Select the first area to be scouted.

  5. Go to the edge of the first area. If it is a field edge go into the field 30 paces. From this starting point, follow the walking instructions for General Sampling Area 1 in the above table:

    Turn right, walk 3 paces, turn back to your original direction, take 19 paces, sample the area in front of you.

  6. Go to the next general sampling area and repeat the process using the second set of walking instructions (General Sampling Area 2 in the table above).


    Through experience you will find that the number of paces specified may be too many or too few to use depending upon field size. If the field is very large, simply multiply the number of paces by 10 or 100. If the field is very small, divide the number of paces by some number (e.g. 10) to keep you from running over the end of a sampling area.

    Remember the objective is to remove bias from your selection of sites. There is nothing magic about these numbers.

    Table 2. 100 Sets of Random Site Selection Directions
    Entry NumberDirection - Left or RightPaces - Left or RightPaces Away
    1Right15
    2Right319
    3Right169
    4Right1724
    5Left1317
    6Right56
    7Left194
    8Left1118
    9Right1416
    10Right720
    11Left257
    12Right2414
    13Right1811
    14Right621
    15Left2025
    16Right151
    17Right2122
    18Left2323
    19Left810
    20Right22
    Entry NumberDirection - Left or RightPaces - Left or RightPaces Away
    21Left2213
    22Right168
    23Right123
    24Left912
    25Left415
    26Right26
    27Right1213
    28Left1122
    29Right711
    30Right414
    31Right315
    32Right213
    33Left164
    34Right1917
    35Left58
    36Right619
    37Left249
    38Right235
    39Right251
    40Right1523
    Entry NumberDirection - Left or RightPaces - Left or RightPaces Away
    41Left824
    42Left1025
    43Left2010
    44Right2216
    45Left120
    46Right97
    47Left132
    48Left1812
    49Left1721
    50Right1418
    51Left113
    52Right619
    53Left1410
    54Left2222
    55Left1311
    56Left312
    57Left1013
    58Right1821
    59Left820
    60Left215
    Entry NumberDirection - Left or RightPaces - Left or RightPaces Away
    61Right1218
    62Left48
    63Right216
    64Right1524
    65Right244
    66Left513
    67Left2323
    68Left714
    69Left1911
    70Left251
    71Left2025
    72Right112
    73Right168
    74Left177
    75Right919
    76Left1024
    77Right66
    78Left715
    79Left85
    80Left1721
    Entry NumberDirection - Left or RightPaces - Left or RightPaces Away
    81Right318
    82Right1817
    83Left252
    84Left2016
    85Left223
    86Right2322
    87Right19
    88Left1610
    89Left241
    90Right1423
    91Left424
    92Left225
    93Left1510
    94Left1916
    95Left1211
    96Right1123
    97Right211
    98Right94
    99Left1318
    100Left521

    Revised: 5/96

    CAUTION! Pesticide recommendations in this publication are registered for use in Kentucky, USA ONLY! The use of some products may not be legal in your state or country. Please check with your local county agent or regulatory official before using any pesticide mentioned in this publication.

    Of course, ALWAYS READ AND FOLLOW LABEL DIRECTIONS FOR SAFE USE OF ANY PESTICIDE!



    This page is maintained by Pat Dillon, Department of Entomology, University of Kentucky. Please send questions or suggestions to: pdillon@uky.edu