The Significance of the Difference Between Two Independent Proportions
RatioDiff computes the same p-values as this stats page. Just Drag and drop your Excel spreadsheet file onto the logo. Two extra sheets will be inserted "z-values" and "p-values"
You can also install this applet as a fully functioning program on your desktop (Look for the logo on your desktop)
Calculation
The computation is based on the comparison of proportions in paired samples. If the proportion of interest in the first sample
is pa = ka/na and that of the paired sample is pb = kb/nb and if
the ki's are not too small or too big and the ni's are not too small (Ratiodiff make no call on the bigness or smallness of the input values - caveat emptor), then by a well known
theorem of statistics the pi's are normally distributed with standard deviation and so is the difference pa - pb. If pa is not so different from pb we can compute
where p is the total proportion (ka + kb)/(na + nb) so that z is normally distributed U(0,1). From this the single tailed p value - the probability that a similar sample of z is greater than *this* z is given by
where erf is the error function
Layout of Excel Spreadsheet
The first sheet should contain the following layout of numbers.The rows should be marked with the keys ka ... kb
etc. Formatting is irrelevent: we use the regular expression (k|n)\\s*([^\\s=]+)\\s*= — that is to say we look for the text k or n followed by some character followed by an equals sign with any spaces in between allowed. The first "column"
will be compared with the others. At the bottom there should be a row giving the totals
marked by na ... nb etc.
| At the top of sheet one.... |
|
| etc. etc. And near the bottom of sheet one.... |
|
This work is licenced under a Creative Commons Licence.
Centre Researcher Sota Fujii part of Rhizanthella Team
Western Australia's Mysterious Underground Orchid Revealed
Rhizanthella gardneri is a cute, quirky and critically endangered orchid that lives all its life underground. It even blooms underground, making it virtually unique amongst plants. Last year, using radioactive tracers, scientists at The University of Western Australia showed that the orchid gets all its nutrients by parasitising fungi associated with the roots of broom bush, a woody shrub of the WA outback. Now, with less than 50 individuals left in the wild, Plant Energy Biology scientists have made a timely and remarkable discovery about its genome.
Read our story in
Link to the UWA media release
Publication:
Centre Researcher Sota Fujii awarded by the JSPS 独立行政法人日本学術振興会
Sota Fujii Awarded:
Plant Energy Biology Research Associate Dr Sota Fujii is off to a terrific start in 2011. Following on from his recent publication (Full Text) in the Proceedings of the National Academy of Sciences (PNAS), he has won both a Japanese research award and a fellowship to continue his valuable work in plant genetics.
Dr Fujii was selected from 300 agricultural scientists for the position of "Super Postdoctoral Fellow" by the Japan Society for the Promotion of Science (JSPS). The fellowship is funded by the Japanese Ministry of Education, Science, Sports and Culture.
I will do my best to use this precious money from Japanese Taxpayers to contribute to the advancement of life science at global level, like my hero Dr. Barbara McClintock,
pledged Dr Fujii.Dr Fujii's research on restorer to fertility genes in plants has also earned him a Inoue Research Award for Young Scientists. This prize for early career scientists highlights the great work being done by this promising young researcher.
