Time vs absorbance data input

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JJ94
Posts: 2
Joined: Mon Mar 10, 2014 12:08 pm

Time vs absorbance data input

Postby JJ94 » Mon Mar 10, 2014 12:27 pm

I've taken an absorbance measurements of 30 samples, each day, over 14 days. The samples are divided into two sets; with a mass of either 3 or 6 (with 15 of each).

The measurements were not taken at the same time every day; so I have them in units of hh:mm (but all the samples were run at the same time as each other).

I'm trying to run a repeated measures ANOVA of this data to determine if there is a significant difference between the two sets (3 or 6). But I'm struggling to get my head around how to input this data.

I have 30 rows; each corresponding to one sample. The absorbance values at one time point are input as a column (14 columns), with an extra column for the mass; either 3 or 6.
But how do I give these columns a time value so the data can be analysed? Or is this the wrong way to input this data?
GerineL
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Joined: Tue Jun 10, 2008 4:50 pm

Re: Time vs absorbance data input

Postby GerineL » Mon Mar 10, 2014 12:54 pm

if you want to use repeated measures, just make sure the first measure of each participant corresponds to the first measure of all others, the second corresponds etc.

so you ignore the exact time, you just use measure1, measure2, measure3 etc. as columns.
JJ94
Posts: 2
Joined: Mon Mar 10, 2014 12:08 pm

Re: Time vs absorbance data input

Postby JJ94 » Mon Mar 10, 2014 1:32 pm

Thanks!

That seems to be working, but I'm missing one value at one time point and it seems to be excluding that entire sample from the analysis.

Is there a way to get it to just ignore the missing value (I've set the Missing value to be 999 & Values to replace 999 with "no value" in the variables options.
GerineL
Moderator
Posts: 1477
Joined: Tue Jun 10, 2008 4:50 pm

Re: Time vs absorbance data input

Postby GerineL » Tue Mar 11, 2014 8:58 am

I don't think so, but see here and search for word "missing"

http://www.uvm.edu/~dhowell/StatPages/M ... asures.pdf

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