What test do I use?

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skippyyy
Posts: 3
Joined: Sun Jan 06, 2013 1:39 pm

What test do I use?

Postby skippyyy » Sun Jan 06, 2013 1:57 pm

Hello

I am working on an assignment and am very stuck on the statistical part. I'm so bad at it!

I was looking at aphid response time to 12 different natural pesticides (at 4 different concentrations each), and noting down how long it took a particular aphid to leave a leaf sample (up until 15 minutes)

I don't think there is any form of hypothesis as I need to see if the results "fit"? Or work well together? So confused

Anyway, I was wondering if anybody would have any idea what test to use?

Thanks
statman
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Re: What test do I use?

Postby statman » Mon Jan 07, 2013 2:42 pm

"fit." what does this mean?

There has to be an hypothesis else hoe do you know what your are testing - Looks like differences in pesticide?

Also, see the Note below
See the note below

NOTE: Please read the Posting Guidelines and always tell us your OS, the SPSS version and information about your study and data!

Statman
Statistical Services
skippyyy
Posts: 3
Joined: Sun Jan 06, 2013 1:39 pm

Re: What test do I use?

Postby skippyyy » Fri Jan 11, 2013 12:32 pm

Well I want to see if they bear statistical significance

I did read; but did not think OS or version came into play as I was not having problems with the program

Thanks for the reply though
statman
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Re: What test do I use?

Postby statman » Fri Jan 11, 2013 2:54 pm

Objective still unclear

OS & SPSS version helps us determine the approach since, e.g., several models exist in V20 but not in V16 so ...
skippyyy
Posts: 3
Joined: Sun Jan 06, 2013 1:39 pm

Re: What test do I use?

Postby skippyyy » Sat Jan 12, 2013 10:30 am

I don't really know how to explain it as I have no idea how to do stats

What would you recommend? And what to look for? My data shows that as the concentration of chemical increases, aphid response time decreases.

I'd like to back that up with numbers as well as references from papers

OS: Windows 7, IBM SPSS v.19

Thanks!
MOram
Posts: 5
Joined: Wed Jan 23, 2013 2:07 pm

Re: What test do I use?

Postby MOram » Fri Jan 25, 2013 12:33 pm

Hi,

i think I get what you're after, and can think of two ways of approaching the issue. The first - and most straightforward - is to do a linear regression.

Use the time as the dependent variable and concentration as the predictor. This will allow you to predict time for any concentration. If you are not familiar with stats, you should go for this option.

A slightly more powerful method is to run an ANOVA (DV = time, fixed factor = concentration) and look at the linear contrast. This method, although not as immediately intuitive, will look for a montonic trend rather than the restricted simple linear trend (but won't allow you to describe the relationship)

Mike

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