Related link :
Sample Size Introduction and Explanation Page
Poisson Distribution and Procedures Explained Page
Introduction
Calculations
Tables
References
Introduction
Comparison of Different Methods of Calculations
General discussions on Poisson distribution and comparing two counts are
provided in the Poisson Distribution and Procedures Explained Page.
Three methods of calculating sample size for comparing two counts are available.
 The Poisson's Test comparing two counts was initially described by Przyborowski and Wilenski
(see reference), and is known as the Conditional Test (the C Test). The test is based on the
null hypothesis that the ratio of the two count rates (λ_{2} / λ_{1}) is equal to
1.
 Krishnamoorthy and Thomson (see reference) proposed an improvement on the C Test,
where the null hypothesis is that the difference between the two count rates
(λ_{2}  λ_{1}) is equal to 0. Althought this
test is more complex, the advantages are that it is both more robust and more powerful, so the
sample size required is smaller than that of the C Test.
 Whitehead (see reference), in his text book on unpaired sequential analysis, provided
algorithms to determine sample sizes for nonsequential methods, and a method for comparing
two counts was also described.
Sample size calculation for the C Test and the E Test are based on the Poisson distribution.
Computation requires multiple nested loops of calculating the Binomial Coefficient, and the computation time increases
exponentially as the sample size increases. Sample size of more than 100 takes a few seconds
to compute, but sample size over 1000 may take up to 30 minutes to compute.
Whitehead's algorithm is based on a transformation, where the difference between the two
count rates (λ_{2}  λ_{1}) is assumed to be a mean of a Normally distributed variable.
The calculation is therefore short, and the samle size calculated is smaller than that for both the C Test and the E Test.
This makes the whitehead approach eadier to use, but the assumption of normal distribution becomes
increadingly inappropriate as the sample size decreases.
Please Note : In StatTools, estimating sample size requirement for comparing two counts uses the one tail model.
For a two tail model, do the same calculation using half the α value. For example, sample size for α=0.05 in a
two tail model is the same as that for α=0.1 in the one tail model, everything else being the same.
The plot to the right shows the relationship between sample sizes required calculated from the 3
algorithms.
The x axis represents sample size calculated by Whitehead's algorithm, and the y axis the percentage difference between
sample sizes calculated from the other two algorithms and that from Whitehead's algorithm.
If the sample size calculated by C or E Test is n_{c/e} and sample size calculated by the whitehead algorithm is
n_{w}, the % Difference = (n_{c/e}  n_{w}) / n_{w} x 100.
It can be seen that sample size for the C Test (in blue) is slightly greater than sample size for the E Test (red), as
the E Test is more powerful and so require a smaller sample size.
The sample size of bothe the C and E Tests are greater than that from Whitehead's algorithm, but the difference
(in term of %) decreases as sample size increases.
The differences between the sample sizes from the 3 algorithm are therefore trivial when the sample size is more
than 100, but becomes relevant under that size.
The table of sample size can therefore be consulted, and the sample size required can be derived from numbers in
the table. If the sample size is over 100, it is probably usable. A more precise sample size should be
calculated using the Javascript program, if the initial sample size is estimated to be less than 100.
Introduction
Javascript Program
Please note that computation may take a long time if the sample size is large. On average, sample size less than 100
takes about 30 seconds. Time increases exponentially so that sample size of 200 may take 120 seconds, and further increase may
take even hours.
Please note that some browsers have time limits, and when that limit is reached it asks the user whether to continue or not.
Although long programs can be run, it does require the user to attend and repeatedly tell the browser to continue. The limits are as follows.
 Internet Explorer  5 million statements
 Firefox  10 secs
 Safari  5 secs
 Chrome  no time limit
 Opera  no time limit
Please note that the calculations are for one tail studies.
Explanation
λ1=0.0010.003, λ2=0.0020.05
λ1=0.0040.006, λ2=0.0050.05
λ1=0.0070.009, λ2=0.0080.05
λ1=0.010.012, λ2=0.0110.05
This section provides a series of tables presenting commonly used sample sizes comparing two count rates.
The tables are for Type I Error (α) of 0.05 for 1 tail, power of 0.8, and assuming that the two groups have similar sample sizes.
The calculations are from Whitehead, C Test, and E Test, as referenced.
Although the tables present only a limited range of λs, the sample size can be extrapolated from the tables, as,
for the same ratio of the two λs, the sample size is proportionate to the λs, as shown in the following table
λ1  λ2  SSiz by Whitehead  SSiz for C Test  SSiz for E Test 
1  2  17  20  19 
0.1  0.2  172  197  186 
0.01  0.02  1716  1964  1863 
0.001  0.002  17158  19637  18631 
It can be seen that, as the lambda value decreases by a tenth, the sample size required increases by ten fold.
Sampe size values between cells in the tables can therefore be calculated by extrapolation between the cells.
Sample size for comparing two count rates (λ1 and λ2) with Poisson distribution.
 Probability of Type I Error (α, 1 tail) = 0.05
 Power (1β)= 0.8
 Assuming equal sample size in the two groups (Ratio n2/n1=1)
 Sample size according to Whitehead's formula (WH), for C Test (C), and E Test (E)
λ1  λ2  WH  C  E  
0.001  0.002  17158  19637  18631  :  λ1  λ2  WH  C  E  
0.001  0.003  5123  6762  5863  :  0.002  0.003  30085  32669  30906  :  λ1  λ2  WH  C  E 
0.001  0.004  2574  3701  3247  :  0.002  0.004  8579  9818  9315  :  0.003  0.004  42688     
0.001  0.005  1591  2473  2192  :  0.002  0.005  4208  5063  4570  :  0.003  0.005  11847  12865  12171 
0.001  0.006  1101  1904  1583  :  0.002  0.006  2561  3380  2931  :  0.003  0.006  5719  6545  6209 
0.001  0.007  817  1510  1269  :  0.002  0.007  1751  2413  2105  :  0.003  0.007  3445  4144  3740 
0.001  0.008  636  1250  1026  :  0.002  0.008  1287  1850  1622  :  0.003  0.008  2337  2948  2674 
0.001  0.009  512  1066  857  :  0.002  0.009  994  1487  1311  :  0.003  0.009  1708  2254  1955 
0.001  0.010  424  908  734  :  0.002  0.010  796  1238  1051  :  0.003  0.010  1313  1810  1579 
0.001  0.011  359  810  641  :  0.002  0.011  655  1094  941  :  0.003  0.011  1047  1443  1259 
0.001  0.012  308  731  551  :  0.002  0.012  550  951  791  :  0.003  0.012  858  1234  1082 
0.001  0.013  269  669  512  :  0.002  0.013  471  841  704  :  0.003  0.013  719  1075  907 
0.001  0.014  237  603  451  :  0.002  0.014  408  754  633  :  0.003  0.014  613  951  808 
0.001  0.015  211  550  402  :  0.002  0.015  359  684  558  :  0.003  0.015  531  825  730 
0.001  0.016  189  514  381  :  0.002  0.016  318  625  513  :  0.003  0.016  465  750  641 
0.001  0.017  171  475  345  :  0.002  0.017  284  575  474  :  0.003  0.017  411  687  590 
0.001  0.018  156  444  316  :  0.002  0.018  256  533  429  :  0.003  0.018  367  634  528 
0.001  0.019  143  422  305  :  0.002  0.019  233  498  389  :  0.003  0.019  330  589  493 
0.001  0.020  131  387  279  :  0.002  0.020  212  454  378  :  0.003  0.020  299  535  464 
0.001  0.021  122  374  261  :  0.002  0.021  195  439  347  :  0.003  0.021  272  503  422 
0.001  0.022  113  348  242  :  0.002  0.022  179  404  320  :  0.003  0.022  249  474  387 
0.001  0.023  105  334  236  :  0.002  0.023  166  385  297  :  0.003  0.023  230  439  358 
0.001  0.024  98  318  221  :  0.002  0.024  154  365  276  :  0.003  0.024  212  416  341 
0.001  0.025  92  304  208  :  0.002  0.025  144  343  266  :  0.003  0.025  197  397  328 
0.001  0.026  87  288  196  :  0.002  0.026  134  333  255  :  0.003  0.026  183  370  305 
0.001  0.027  82  280  194  :  0.002  0.027  126  314  240  :  0.003  0.027  171  355  286 
0.001  0.028  77  264  183  :  0.002  0.028  119  296  226  :  0.003  0.028  160  342  268 
0.001  0.029  73  258  174  :  0.002  0.029  112  292  214  :  0.003  0.029  150  321  258 
0.001  0.030  69  245  171  :  0.002  0.030  106  276  202  :  0.003  0.030  142  304  246 
0.001  0.031  66  241  163  :  0.002  0.031  100  266  191  :  0.003  0.031  134  295  239 
0.001  0.032  63  230  156  :  0.002  0.032  95  258  191  :  0.003  0.032  126  284  225 
0.001  0.033  60  226  150  :  0.002  0.033  90  245  181  :  0.003  0.033  120  271  214 
0.001  0.034  57  216  148  :  0.002  0.034  86  235  173  :  0.003  0.034  114  263  203 
0.001  0.035  55  208  142  :  0.002  0.035  82  232  165  :  0.003  0.035  108  256  193 
0.001  0.036  52  203  136  :  0.002  0.036  78  222  158  :  0.003  0.036  103  244  184 
0.001  0.037  50  200  130  :  0.002  0.037  75  213  151  :  0.003  0.037  98  233  181 
0.001  0.038  48  192  126  :  0.002  0.038  72  208  146  :  0.003  0.038  94  224  174 
0.001  0.039  46  185  124  :  0.002  0.039  69  203  146  :  0.003  0.039  90  223  171 
0.001  0.040  45  181  121  :  0.002  0.040  66  195  140  :  0.003  0.040  86  214  163 
0.001  0.041  43  177  117  :  0.002  0.041  63  193  135  :  0.003  0.041  82  204  156 
0.001  0.042  41  174  116  :  0.002  0.042  61  186  130  :  0.003  0.042  79  201  151 
0.001  0.043  40  170  113  :  0.002  0.043  59  181  126  :  0.003  0.043  76  197  145 
0.001  0.044  39  165  110  :  0.002  0.044  57  175  122  :  0.003  0.044  73  190  139 
0.001  0.045  37  158  105  :  0.002  0.045  55  174  118  :  0.003  0.045  71  184  135 
0.001  0.046  36  157  103  :  0.002  0.046  53  168  118  :  0.003  0.046  68  178  130 
0.001  0.047  35  153  102  :  0.002  0.047  51  163  114  :  0.003  0.047  66  175  126 
0.001  0.048  34  149  100  :  0.002  0.048  49  159  111  :  0.003  0.048  63  171  126 
0.001  0.049  33  147  97  :  0.002  0.049  48  154  108  :  0.003  0.049  61  166  122 
0.001  0.050  32  143  94  :  0.002  0.050  46  152  104  :  0.003  0.050  59  160  118 
Sample size for comparing two count rates (λ1 and λ2) with Poisson distribution.
 Probability of Type I Error (α, 1 tail) = 0.05
 Power (1β)= 0.8
 Assuming equal sample size in the two groups (Ratio n2/n1=1)
 Sample size according to Whitehead's formula (WH), for C Test (C), and E Test (E)
λ1  λ2  WH  C  E  
0.004  0.005  55185      :  λ1  λ2  WH  C  E  :  
0.004  0.006  15043  16334  15453  :  0.005  0.006  67633      :  λ1  λ2  WH  C  E 
0.004  0.007  7179  8215  7375  :  0.005  0.007  18204      :  0.006  0.007  80056     
0.004  0.008  4290  4909  4657  :  0.005  0.008  8612  9352  8847  :  0.006  0.008  21344     
0.004  0.009  2893  3480  3142  :  0.005  0.009  5113  5850  5252  :  0.006  0.009  10029  10890  10302 
0.004  0.010  2104  2532  2285  :  0.005  0.010  3432  3928  3726  :  0.006  0.010  5924  6433  6086 
0.004  0.011  1611  2032  1842  :  0.005  0.011  2487  2991  2700  :  0.006  0.011  3960  4532  4069 
0.004  0.012  1281  1690  1466  :  0.005  0.012  1898  2284  2061  :  0.006  0.012  2860  3273  3105 
0.004  0.013  1047  1382  1258  :  0.005  0.013  1505  1898  1634  :  0.006  0.013  2177  2618  2364 
0.004  0.014  876  1207  1053  :  0.005  0.014  1228  1550  1405  :  0.006  0.014  1723  2073  1871 
0.004  0.015  745  1070  896  :  0.005  0.015  1025  1352  1173  :  0.006  0.015  1403  1688  1523 
0.004  0.016  644  926  811  :  0.005  0.016  871  1150  997  :  0.006  0.016  1169  1474  1337 
0.004  0.017  563  841  710  :  0.005  0.017  751  1035  903  :  0.006  0.017  992  1252  1135 
0.004  0.018  497  744  655  :  0.005  0.018  656  905  789  :  0.006  0.018  854  1127  978 
0.004  0.019  443  687  585  :  0.005  0.019  578  830  695  :  0.006  0.019  745  983  852 
0.004  0.020  398  619  526  :  0.005  0.020  515  740  648  :  0.006  0.020  656  904  789 
0.004  0.021  360  581  496  :  0.005  0.021  462  665  583  :  0.006  0.021  584  804  702 
0.004  0.022  328  548  471  :  0.005  0.022  418  625  527  :  0.006  0.022  523  721  629 
0.004  0.023  300  502  431  :  0.005  0.023  380  590  501  :  0.006  0.023  473  679  569 
0.004  0.024  275  474  395  :  0.005  0.024  347  539  458  :  0.006  0.024  429  617  540 
0.004  0.025  254  454  379  :  0.005  0.025  318  495  438  :  0.006  0.025  392  564  494 
0.004  0.026  236  421  353  :  0.005  0.026  294  474  404  :  0.006  0.026  360  538  454 
0.004  0.027  219  391  339  :  0.005  0.027  272  454  376  :  0.006  0.027  332  497  438 
0.004  0.028  204  377  316  :  0.005  0.028  253  422  363  :  0.006  0.028  307  476  404 
0.004  0.029  191  363  297  :  0.005  0.029  236  395  339  :  0.006  0.029  285  443  376 
0.004  0.030  179  341  278  :  0.005  0.030  220  380  317  :  0.006  0.030  265  426  364 
0.004  0.031  169  322  271  :  0.005  0.031  207  358  298  :  0.006  0.031  248  399  341 
0.004  0.032  159  312  256  :  0.005  0.032  194  346  290  :  0.006  0.032  232  374  320 
0.004  0.033  150  302  250  :  0.005  0.033  183  327  273  :  0.006  0.033  218  364  313 
0.004  0.034  142  287  237  :  0.005  0.034  173  318  268  :  0.006  0.034  206  345  296 
0.004  0.035  135  273  225  :  0.005  0.035  164  302  254  :  0.006  0.035  194  324  279 
0.004  0.036  128  266  215  :  0.005  0.036  155  294  241  :  0.006  0.036  184  317  265 
0.004  0.037  122  260  204  :  0.005  0.037  147  279  228  :  0.006  0.037  174  301  251 
0.004  0.038  116  248  199  :  0.005  0.038  140  267  218  :  0.006  0.038  165  293  246 
0.004  0.039  111  238  192  :  0.005  0.039  133  259  214  :  0.006  0.039  157  280  235 
0.004  0.040  106  232  188  :  0.005  0.040  127  249  211  :  0.006  0.040  150  268  232 
0.004  0.041  102  224  182  :  0.005  0.041  122  246  203  :  0.006  0.041  143  263  221 
0.004  0.042  97  218  172  :  0.005  0.042  116  234  193  :  0.006  0.042  136  252  211 
0.004  0.043  94  212  168  :  0.005  0.043  112  227  187  :  0.006  0.043  130  247  202 
0.004  0.044  90  203  160  :  0.005  0.044  107  216  179  :  0.006  0.044  125  237  194 
0.004  0.045  86  198  154  :  0.005  0.045  103  213  172  :  0.006  0.045  120  229  187 
0.004  0.046  83  196  148  :  0.005  0.046  99  210  165  :  0.006  0.046  115  219  184 
0.004  0.047  80  190  143  :  0.005  0.047  95  202  159  :  0.006  0.047  110  215  177 
0.004  0.048  77  183  138  :  0.005  0.048  91  194  157  :  0.006  0.048  106  208  171 
0.004  0.049  75  178  134  :  0.005  0.049  88  189  152  :  0.006  0.049  102  206  170 
0.004  0.050  72  172  133  :  0.005  0.050  85  186  151  :  0.006  0.050  98  197  163 
Sample size for comparing two count rates (λ1 and λ2) with Poisson distribution.
 Probability of Type I Error (α, 1 tail) = 0.05
 Power (1β)= 0.8
 Assuming equal sample size in the two groups (Ratio n2/n1=1)
 Sample size according to Whitehead's formula (WH), for C Test (C), and E Test (E)
λ1  λ2  WH  C  E  
0.007  0.008  92464      :  λ1  λ2  WH  C  E  
0.007  0.009  24473      :  0.008  0.009  104861      :  λ1  λ2  WH  C  E 
0.007  0.010  11435  12417  11747  :  0.008  0.010  27593      :  0.009  0.010  117252     
0.007  0.011  6725  7303  6909  :  0.008  0.011  12835      :  0.009  0.011  30707     
0.007  0.012  4481  5127  4603  :  0.008  0.012  7522  8167  7726  :  0.009  0.012  14230     
0.007  0.013  3227  3693  3315  :  0.008  0.013  4996  5425  5132  :  0.009  0.013  8313  9026  8539 
0.007  0.014  2451  2804  2660  :  0.008  0.014  3590  4107  3688  :  0.009  0.014  5508  5981  5658 
0.007  0.015  1935  2327  2101  :  0.008  0.015  2721  3114  2954  :  0.009  0.015  3949  4288  4057 
0.007  0.016  1574  1894  1709  :  0.008  0.016  2145  2455  2328  :  0.009  0.016  2988  3419  3070 
0.007  0.017  1309  1575  1421  :  0.008  0.017  1741  2094  1890  :  0.009  0.017  2352  2692  2485 
0.007  0.018  1109  1398  1204  :  0.008  0.018  1447  1740  1571  :  0.009  0.018  1907  2182  2069 
0.007  0.019  954  1204  1091  :  0.008  0.019  1224  1473  1329  :  0.009  0.019  1582  1903  1717 
0.007  0.020  831  1048  950  :  0.008  0.020  1052  1266  1143  :  0.009  0.020  1338  1609  1453 
0.007  0.021  732  966  838  :  0.008  0.021  916  1154  1047  :  0.009  0.021  1148  1382  1247 
0.007  0.022  651  859  745  :  0.008  0.022  806  1017  921  :  0.009  0.022  999  1202  1085 
0.007  0.023  583  769  700  :  0.008  0.023  716  945  819  :  0.009  0.023  878  1107  954 
0.007  0.024  526  725  632  :  0.008  0.024  641  845  733  :  0.009  0.024  779  981  890 
0.007  0.025  477  658  573  :  0.008  0.025  577  762  660  :  0.009  0.025  697  879  796 
0.007  0.026  435  624  523  :  0.008  0.026  524  692  600  :  0.009  0.026  628  828  718 
0.007  0.027  399  573  480  :  0.008  0.027  478  659  575  :  0.009  0.027  569  750  650 
0.007  0.028  368  530  463  :  0.008  0.028  438  603  526  :  0.009  0.028  519  685  593 
0.007  0.029  340  489  428  :  0.008  0.029  403  555  484  :  0.009  0.029  476  629  545 
0.007  0.030  316  472  399  :  0.008  0.030  373  535  448  :  0.009  0.030  438  603  526 
0.007  0.031  294  440  387  :  0.008  0.031  346  497  417  :  0.009  0.031  404  556  485 
0.007  0.032  275  426  361  :  0.008  0.032  322  463  405  :  0.009  0.032  375  517  450 
0.007  0.033  257  399  339  :  0.008  0.033  301  433  378  :  0.009  0.033  349  481  420 
0.007  0.034  242  376  319  :  0.008  0.034  281  419  354  :  0.009  0.034  326  468  392 
0.007  0.035  228  354  301  :  0.008  0.035  264  395  333  :  0.009  0.035  305  438  367 
0.007  0.036  215  345  295  :  0.008  0.036  249  372  327  :  0.009  0.036  286  412  360 
0.007  0.037  203  327  280  :  0.008  0.037  235  364  309  :  0.009  0.037  269  387  338 
0.007  0.038  192  321  265  :  0.008  0.038  222  345  294  :  0.009  0.038  254  379  321 
0.007  0.039  182  304  261  :  0.008  0.039  210  326  277  :  0.009  0.039  240  359  303 
0.007  0.040  173  289  248  :  0.008  0.040  199  319  273  :  0.009  0.040  227  339  298 
0.007  0.041  165  283  237  :  0.008  0.041  189  304  259  :  0.009  0.041  215  333  282 
0.007  0.042  157  271  226  :  0.008  0.042  180  290  248  :  0.009  0.042  205  318  270 
0.007  0.043  150  259  223  :  0.008  0.043  172  278  237  :  0.009  0.043  195  302  257 
0.007  0.044  144  257  215  :  0.008  0.044  164  273  235  :  0.009  0.044  186  289  246 
0.007  0.045  138  246  206  :  0.008  0.045  157  262  225  :  0.009  0.045  177  284  243 
0.007  0.046  132  236  197  :  0.008  0.046  150  251  215  :  0.009  0.046  169  271  232 
0.007  0.047  127  227  196  :  0.008  0.047  144  241  207  :  0.009  0.047  162  261  223 
0.007  0.048  122  224  189  :  0.008  0.048  138  238  199  :  0.009  0.048  155  250  213 
0.007  0.049  117  216  181  :  0.008  0.049  132  228  196  :  0.009  0.049  149  248  205 
0.007  0.050  112  213  175  :  0.008  0.050  127  226  189  :  0.009  0.050  143  238  205 
Sample size for comparing two count rates (λ1 and λ2) with Poisson distribution.
 Probability of Type I Error (α, 1 tail) = 0.05
 Power (1β)= 0.8
 Assuming equal sample size in the two groups (Ratio n2/n1=1)
 Sample size according to Whitehead's formula (WH), for C Test (C), and E Test (E)
λ1  λ2  WH  C  E  
0.010  0.011  129638      :  λ1  λ2  WH  C  E  
0.010  0.012  33817      :  0.011  0.012  142020      :  λ1  λ2  WH  C  E 
0.010  0.013  15621      :  0.011  0.013  36924      :  0.012  0.013  154400     
0.010  0.014  9102      :  0.011  0.014  17009      :  0.012  0.014  40028     
0.010  0.015  6017  6533  6180  :  0.011  0.015  9888      :  0.012  0.015  18395     
0.010  0.016  4306  4676  4424  :  0.011  0.016  6524  7084  6702  :  0.012  0.016  10672     
0.010  0.017  3253  3721  3341  :  0.011  0.017  4661  5061  4787  :  0.012  0.017  7029  7631  7219 
0.010  0.018  2557  2925  2626  :  0.011  0.018  3516  3819  3613  :  0.012  0.018  5014  5444  5150 
0.010  0.019  2070  2369  2247  :  0.011  0.019  2760  3158  2835  :  0.012  0.019  3778  4102  3881 
0.010  0.020  1716  1964  1863  :  0.011  0.020  2232  2554  2293  :  0.012  0.020  2962  3217  3043 
0.010  0.021  1449  1742  1572  :  0.011  0.021  1849  2115  2006  :  0.012  0.021  2393  2737  2458 
0.010  0.022  1243  1494  1349  :  0.011  0.022  1560  1785  1693  :  0.012  0.022  1980  2266  2035 
0.010  0.023  1080  1300  1173  :  0.011  0.023  1337  1607  1450  :  0.012  0.023  1670  1911  1812 
0.010  0.024  949  1141  1030  :  0.011  0.024  1161  1396  1261  :  0.012  0.024  1430  1637  1552 
0.010  0.025  842  1013  914  :  0.011  0.025  1019  1225  1106  :  0.012  0.025  1241  1492  1346 
0.010  0.026  753  949  818  :  0.011  0.026  904  1088  982  :  0.012  0.026  1089  1309  1182 
0.010  0.027  678  855  775  :  0.011  0.027  807  971  876  :  0.012  0.027  965  1160  1048 
0.010  0.028  614  775  702  :  0.011  0.028  727  915  789  :  0.012  0.028  861  1036  935 
0.010  0.029  560  739  640  :  0.011  0.029  658  829  752  :  0.012  0.029  775  932  841 
0.010  0.030  512  676  587  :  0.011  0.030  599  755  684  :  0.012  0.030  702  845  763 
0.010  0.031  471  621  538  :  0.011  0.031  549  692  627  :  0.012  0.031  639  805  694 
0.010  0.032  435  574  497  :  0.011  0.032  505  665  576  :  0.012  0.032  584  736  667 
0.010  0.033  404  533  485  :  0.011  0.033  466  614  533  :  0.012  0.033  537  677  613 
0.010  0.034  376  518  452  :  0.011  0.034  432  571  494  :  0.012  0.034  496  626  567 
0.010  0.035  350  482  421  :  0.011  0.035  402  531  460  :  0.012  0.035  459  605  525 
0.010  0.036  328  452  394  :  0.011  0.036  375  495  450  :  0.012  0.036  427  563  489 
0.010  0.037  308  425  371  :  0.011  0.037  350  482  421  :  0.012  0.037  398  526  455 
0.010  0.038  289  415  348  :  0.011  0.038  329  452  395  :  0.012  0.038  373  492  426 
0.010  0.039  273  392  329  :  0.011  0.039  309  425  370  :  0.012  0.039  349  461  419 
0.010  0.040  258  371  324  :  0.011  0.040  291  401  350  :  0.012  0.040  328  451  394 
0.010  0.041  244  351  307  :  0.011  0.041  275  394  330  :  0.012  0.041  309  424  370 
0.010  0.042  231  344  291  :  0.011  0.042  260  373  313  :  0.012  0.042  292  402  350 
0.010  0.043  220  328  278  :  0.011  0.043  247  354  297  :  0.012  0.043  276  380  331 
0.010  0.044  209  313  264  :  0.011  0.044  234  337  294  :  0.012  0.044  262  361  315 
0.010  0.045  199  297  261  :  0.011  0.045  223  321  280  :  0.012  0.045  249  357  299 
0.010  0.046  190  295  250  :  0.011  0.046  212  305  267  :  0.012  0.046  236  339  284 
0.010  0.047  181  280  238  :  0.011  0.047  202  301  255  :  0.012  0.047  225  323  271 
0.010  0.048  174  270  230  :  0.011  0.048  193  289  243  :  0.012  0.048  215  309  269 
0.010  0.049  166  258  219  :  0.011  0.049  185  276  243  :  0.012  0.049  205  295  258 
0.010  0.050  159  255  218  :  0.011  0.050  177  274  233  :  0.012  0.050  196  282  247 
Przyborowski J and Wilenski H (1940) Homogeneity of results in testing samples
from Poisson series. Biometrika 31:313323.
Krishnamoorthy, K and Thomson, J. (2004). A more powerful test for comparing
two Poisson means. Journal of Statistical Planning and Inference, 119, 249267.
Program adapted from FORTRAN program by Krishnamoorthy and Thomson, downloaded from
www.ucs.louisiana.edu/~kxk4695/
Whitehead John (1992). The Design and Analysis of Sequential Clinical Trials
(Revised 2nd. Edition) . John Wiley & Sons Ltd., Chichester, ISBN 0 47197550 8. p. 4850
