am in need of some very urgent help! My dissertation is due in on Monday and i have just come across something which means I have an awful lot of changes to make!

My hypothesis for my study is (i believe) one tailed;

**Horses which win the Epsom Derby will have a significantly better stud career than horses which are placed in the Epsom Derby regardless of racing career performance.**

However, i have never been taught or shown any examples using a one tailed hypothesis so i have been blissfully pottering along using spss to analyse my data and looking at the Asymp. Sig. (2-tailed) for my mann whitney U tests and Sig. (2-tailed) for my independent samples t-tests, because that was what the university tutorials said. HOWEVER i have just been flicking through

*discovering statistics using SPSS*(Field 2005) and it says that if the hypothesis is one tailed, the sig. value in the t-test should be devided by 2 to give the one tailed significance. So I go back through the university tutorials for some advice but they are all two tailed examples problem that I'm having now is;

a) i might be reporting the wrong p values

b) as deviding my 2 tailed p values by 2 would leave them <0.05 this would change many of my results; making lots of relationships significant where they currently are not (which would be a good thing in my case!)

c) i might be looking like an utter idiot as i have been writing my hypothesis in all it's one tailed obviousness but reporting two tailed significances!

soo...

any advice? I cannot get in touch with my supervisor and my thesis is due on Monday! I am confident I could change all the data in the time but dont know whether I should :S realistically, I could change my hypothesis to;

**There will be a significant difference between the stud careers of horses which win the Epsom Derby and horses which are placed in the Epsom Derby regardless of racing career performance.**

but i dont know whether this would be acceptable or not :/ I read somewhere that many researchers suggest that one tailed hypotheses should only be used in unavoidable circumstance;

e.g. the height of 15 year old girls will be signifiantly greater than the height of 2 year old girls

so that confuses me even more as to whether I should change it!

Apologies if this makes little sense, I am incredibly rushed and stressed after this little discovery!

Any advice would be appreciated,

Elle