mayfly nymph reproduction rate

[nicola]

my hypothesis is there are greater no of mayfly nymphs at areas with a fast flow rate (site A) than at an area (site B) at a slower one. What stats test do i do??Plz help!thankzz

[mith]

Does your teacher ask you to do actual experiments or to use available texts?

[nicola]

We have to do the experiment!So basicaly I have one site of fast flowing water and 6 samples and another site of slower flow rate with 6 samples. Does that make sense?What stats test do I use?Thankz

[RobJim]

This sounds like a really hard experiment. This website says that the mayfly nymphs live in little burrows, under rocks, and among plants:

http://www.bugsurvey.nsw.gov.au/html/popups/bpedia_02_vsens_ma-ny-a.html

This means that you can't just get some water and then count the nymphs in it. I don't know how you'd go about determining what the concentration of nymphs is at a certain place.

[DevGrp]

So I would sample a series of fast and slow flow areas for a set time and then compare the numbers from the two groups. I'm not sure HOW you would count them but...

As you only have two different data sets to compare then you want to do a T test.

If you had condition A(fast), B(slow) and C (intermediate) then you might want toconsider an ANOVA, which is better than doing lots of individual T tests.


T test assumes that your samples are normally distrubuted, If they aren't then you would have to do a Mann Whitney test.

You can do a t test using Excel and the Ttest fucntion command (see the help)


hope this answers your question?

[mith]

How long do you have to do this experiment?

[nicola]

I have a week to do my whole coursework!Thankz so much 4 all of ur help. I need to do a Mann Whitney U test. I was wondering what limitations would I need to talk about when doing this kind of experiment?That bit is realy hard! Thankz alot!