# two-factor factorial design

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I'm doing "two-factor factorial design" on spss but having trouble with geting out puts

Post hoc tests are not performed for Date because error term has zero degrees of freedom.

Post hoc tests are not performed for SamplePoint because error term has zero degrees of freedom.

All absolute deviations are constant within each cell. Levene F statistics cannot be computed.

these error messages are appearing

what could be the reason

Post hoc tests are not performed for Date because error term has zero degrees of freedom.

Post hoc tests are not performed for SamplePoint because error term has zero degrees of freedom.

All absolute deviations are constant within each cell. Levene F statistics cannot be computed.

these error messages are appearing

what could be the reason

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#2

(Original post by

I'm doing "two-factor factorial design" on spss but having trouble with geting out puts

Post hoc tests are not performed for Date because error term has zero degrees of freedom.

Post hoc tests are not performed for SamplePoint because error term has zero degrees of freedom.

All absolute deviations are constant within each cell. Levene F statistics cannot be computed.

these error messages are appearing

what could be the reason

**Narendran**)I'm doing "two-factor factorial design" on spss but having trouble with geting out puts

Post hoc tests are not performed for Date because error term has zero degrees of freedom.

Post hoc tests are not performed for SamplePoint because error term has zero degrees of freedom.

All absolute deviations are constant within each cell. Levene F statistics cannot be computed.

these error messages are appearing

what could be the reason

1

reply

(Original post by

I'd need to know a few more specifics about what you're doing, but it sounds as if you have level combinations with too few elements.

**Gregorius**)I'd need to know a few more specifics about what you're doing, but it sounds as if you have level combinations with too few elements.

parameters are pH, Turbidity dissolved oxygen, biological oxygen demand, Fe, Nitrate, Ammonia content, etc

5 sampling points, done sampling for 5 months(monthly)

Objectives

• To find the reasons for the water quality changes with time on a certain point

• To find the reasons for the water quality changes along the stretch at a certain time

is this information enough?

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#4

(Original post by

doing a river water quality monitoring

parameters are pH, Turbidity dissolved oxygen, biological oxygen demand, Fe, Nitrate, Ammonia content, etc

5 sampling points, done sampling for 5 months(monthly)

Objectives

• To find the reasons for the water quality changes with time on a certain point

• To find the reasons for the water quality changes along the stretch at a certain time

is this information enough?

**Narendran**)doing a river water quality monitoring

parameters are pH, Turbidity dissolved oxygen, biological oxygen demand, Fe, Nitrate, Ammonia content, etc

5 sampling points, done sampling for 5 months(monthly)

Objectives

• To find the reasons for the water quality changes with time on a certain point

• To find the reasons for the water quality changes along the stretch at a certain time

is this information enough?

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(Original post by

What analyses are you attempting to perform?

**Gregorius**)What analyses are you attempting to perform?

I have never learned stat, so I have no idea which I must choose

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#6

(Original post by

That's where I'm stuck

I have never learned stat, so I have no idea which I must choose

**Narendran**)That's where I'm stuck

I have never learned stat, so I have no idea which I must choose

So let me see if I understand exactly the data that you have collected. If I’m reading you correctly, you are measuring:

(i) at least six parameters (pH, Turbidity dissolved oxygen, biological oxygen demand, Fe, Nitrate, Ammonia content, etc)

(ii) at five geographically separated locations in a river (your sampling points).

(iii) each at five different times (monthly for five months).

So for each parameter (such as pH), you have 25 measurements. Is that correct?

Now, you’ve also given me two objectives that involve a quantity called “water quality”. Can you tell me what the definition of this is?

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you perfectly understood

"water quality" just means the parameters I'm checking, nothing else

I've attached the stat methodology of a similar research

but I cant understand in which order these must be done

can you help me with that

"water quality" just means the parameters I'm checking, nothing else

I've attached the stat methodology of a similar research

but I cant understand in which order these must be done

can you help me with that

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#8

(Original post by

you perfectly understood

"water quality" just means the parameters I'm checking, nothing else

I've attached the stat methodology of a similar research

but I cant understand in which order these must be done

can you help me with that

**Narendran**)you perfectly understood

"water quality" just means the parameters I'm checking, nothing else

I've attached the stat methodology of a similar research

but I cant understand in which order these must be done

can you help me with that

To be honest, I think you’re going to need local statistical help – the paper that you’ve quoted is using quite advanced techniques (PCA and cluster analysis) that really need quite a lot of statistical knowledge to do properly. I’m also worried that you don’t have enough data to apply these sorts of techniques.

If we go back to your first objective: “To find the reasons for the water quality changes with time on a certain point” then for each parameter (let’s take pH, for example) you have 5 measurement at each location. You could (only just, this is a very small sample size) do a linear regression with pH as outcome and with time value as explanatory variable at each location. This would tell you whether pH was changing over time separately at each location. You could instead assume that the same processes are happening at all the locations and lump the data together by time – this gives you 25 observations, and linear regression would be OK with this sample size. You would lose the differentiation between locations though.

But you have many more than one parameter measured at each location, and this is where I suspect that you’re meant to use PCA or cluster analysis. Instead of either (a) using each parameter separately in a regression or (b) doing a fully multivariate analysis (i.e. taking the vector of all parameter measurements as outcome), the idea here is that you take all the different types of parameter measurement and you reduce their dimension using PCA or cluster analysis, and then you stick this reduced outcome variable into a regression. But, as I say, this is hard stuff!

For your second objective: “To find the reasons for the water quality changes along the stretch at a certain time”, I’m not at all how you would do this unless you had some sort of additional spatial model of how the different locations interact.

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[QUOTE=Gregorius;74462048]To be honest, I think you’re going to need local statistical help – the paper that you’ve quoted is using quite advanced techniques (PCA and cluster analysis) that really need quite a lot of statistical knowledge to do properly. I’m also worried that you don’t have enough data to apply these sorts of techniques.

so then ill use regression for each parameter separately for the 1st objective

for the second one I'll ask my research supervisor

thanks a lot for your time

so then ill use regression for each parameter separately for the 1st objective

for the second one I'll ask my research supervisor

thanks a lot for your time

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I have a doubt again

in the regression, i can input 1 dependent variable and many independent variables. but for me, the "parameters" are dependent variable & independent variables are time (sample collection dates) & the sampling points.

how can I input the time (dates) as the independent variable and my parameters as dependent variables

in the regression, i can input 1 dependent variable and many independent variables. but for me, the "parameters" are dependent variable & independent variables are time (sample collection dates) & the sampling points.

how can I input the time (dates) as the independent variable and my parameters as dependent variables

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I was thinking to input the sampling points by taking the upstream point as "0" & then the next ones with the length from the first point

will it be ok to do in such way?

if I want to do in that way how should I input them?

even though there is another issue, for each date or sample point there will be 5 sets of data

how to deal with that?

will it be ok to do in such way?

if I want to do in that way how should I input them?

even though there is another issue, for each date or sample point there will be 5 sets of data

how to deal with that?

0

reply

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#13

(Original post by

I have a doubt again

in the regression, i can input 1 dependent variable and many independent variables. but for me, the "parameters" are dependent variable & independent variables are time (sample collection dates) & the sampling points.

how can I input the time (dates) as the independent variable and my parameters as dependent variables

**Narendran**)I have a doubt again

in the regression, i can input 1 dependent variable and many independent variables. but for me, the "parameters" are dependent variable & independent variables are time (sample collection dates) & the sampling points.

how can I input the time (dates) as the independent variable and my parameters as dependent variables

0

reply

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#14

(Original post by

I was thinking to input the sampling points by taking the upstream point as "0" & then the next ones with the length from the first point

will it be ok to do in such way?

if I want to do in that way how should I input them?

even though there is another issue, for each date or sample point there will be 5 sets of data

how to deal with that?

**Narendran**)I was thinking to input the sampling points by taking the upstream point as "0" & then the next ones with the length from the first point

will it be ok to do in such way?

if I want to do in that way how should I input them?

even though there is another issue, for each date or sample point there will be 5 sets of data

how to deal with that?

0

reply

Report

#15

(Original post by

cant i do a principal component analysis

**Narendran**)cant i do a principal component analysis

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