comparison of slopes

[#1]

After running an ANCOVA model with more than two values of the categorical variable, how can I perform pairwise comparisons of slopes?

Hillary.

[#2]

Hi Hillary,

I just uploaded a new version (v0.04) that should be more robust with numbered levels.

Julian

[#3]

Hi Julian,

I'm afraid v04 gives the same output as the previous versions for numbered

categories.

Hillary.

From: julian

Sent: Friday, May 27, 2016 9:23 PM

To: Hillary Voet <hillary.voet@mail.huji.ac.il>

Subject: Re: - comparison of slopes

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comparison of slopes

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[#4]

How interesting! We'll get to the bottom of this.  Here are a few things to try:

1. On the dataset that is failing, check to see if value ordering is set for your factor (the numbered column)--Right click the column > Column Info, then see if there is a value ordering set under the properties. If Value Ordering it set, does it appear to be blank? Delete that property and try the add-in again. If it now works I think I know what was going on.
2. If that doesn't work, do you have another dataset with similar properties that you could try? I'd like to test the possibility that it's something specific to the dataset you're working with.
3. If you don't have another data set with this arrangement, would you try with this test data set I've attached here? This has the same arrangement (numeric but nominal factor) and works on my side on both windows and mac.

[#5]

Hi Julian,

Curioser and curioser.

1. Your data set worked perfectly.

2. On my original data set I checked the Value Ordering and found

that is was ordered naturally.

3. I tried removing this ordering, but with or without it I don't get

the full set of comparisons. In some versions I don't get any output from

your add-in and in some I get only the standard reference category.

4. Tried another numerical variable which I defined as Nominal: ditto.

5. Created a new, small data set of my own. Again, the numerical

categorical variable gave me only a single reference category. This was the

same whether I defined it as Character-Nominal or Numerical-Nominal.

6. I am using JMP 12 on Windows 7.

Can you help?

Thanks,

Hillary.

From: julian

Sent: Saturday, May 28, 2016 8:15 PM

To: Hillary Voet <hillary.voet@mail.huji.ac.il>

Subject: Re: - comparison of slopes

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comparison of slopes

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[#6]

Hi Julian,

In addition to my last letter:

I tried adding a fourth category to your test data set. When I ran the

add-in I only got results for categories 1, 2 and 3 as reference

categories. Could you use this information to solve the puzzle?

Hillary.

From: julian

Sent: Saturday, May 28, 2016 8:15 PM

To: Hillary Voet <hillary.voet@mail.huji.ac.il>

Subject: Re: - comparison of slopes

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comparison of slopes

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[#7]

Hi Hillary,

Curiouser and curiouser, indeed!  I haven't been able to crack this yet, nor can I get this exact behavior to replicate on my side (on mac, or windows 8). It's especially odd that we're getting inconsistent failing! It might help to see what error messages you are getting reported to the log (View menu > Log). It will be most helpful if you clear the contents of the log before running the add-in (Edit > Clear), and then after running the add-in, if it fails, save the log to a file and attach it here. That should give me some sense of where things are failing. 

Julian

[#8]

Hi Julian,

There wasn't anything in the log. I am attaching the adapted data set, the

Fit Model output and the results after running the add-in.

Thanks,

Hillary.

From: julian

Sent: Wednesday, June 01, 2016 9:20 PM

To: Hillary Voet <hillary.voet@mail.huji.ac.il>

Subject: Re: - comparison of slopes

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comparison of slopes

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[#9]

Hi Hillary,

That helped! I think I tracked down one issue and just updated the add-in (v0.05). What happened there is there was only a partial list of levels in the value ordering since you added a level after the ordering had been set. In the new version of the add-in the initial settings for value ordering aren't taken from the column property but are found by making a list of every unique level of the categorical factor. This should be more robust to these issues. Hopefully this is one curiosity settled... let me know if this now works for you.

Julian

[#10]

Hi Julian,

Brilliant! The add in now works when the categorical variable has numerical

values.

Many, many thanks,

Hillary.

From: julian

Sent: Thursday, June 02, 2016 8:55 PM

To: Hillary Voet <hillary.voet@mail.huji.ac.il>

Subject: Re: - comparison of slopes

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comparison of slopes

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[#11]

Excellent! I'm so glad we figured this out