Why does a bipolar scale need indifference at zero?

Discuss statistics related things
Post Reply
Whirly123
Posts: 31
Joined: Mon May 06, 2019 3:07 pm

Why does a bipolar scale need indifference at zero?

Post by Whirly123 »

We have a bipolar scale that asks do you agree with A more or b more

It happened to be coded this way
(1) completely agree with A <--> (7) completely agree with B
So (4) is indifference

It should have been coded this way:
(-3) completely agree with A <--> (3) completely agree with B
So (0 is indifference)

In a regression our agreement scale is a control to see whether the difference between two conditions can be explained by agreement. E.g. person A seems to be liked significantly more, is this just because most people agree person A more than person B. (Agree is the control Like is DV).
sfsdfwe.jpg
sfsdfwe.jpg (19.98 KiB) Viewed 2744 times
You can see the graphs are the same but the numbers at the x axis are different because of the different coding. But for the graph on the left there is a significant main effect of condition (p < .001) and on the right the main effect disappears (p = 0.546) (i.e. is explained by agreement)

I know the right one is correct but I didn't realise the coding would make a difference in regression. Can anyone explain why I need to make sure indifference is at 0 on bipolar scales? The only thing I can think of is that -3 and 3 have the same absolute value
but 1 and 7 don't but I am not sure why absolute value needs to be calculated.
simonmoon
Posts: 17
Joined: Thu Oct 27, 2022 3:45 pm

Re: Why does a bipolar scale need indifference at zero?

Post by simonmoon »

It seems the issue is related to centering, not the scale scoring. But, if you show me your regression model, I can figure out the reason.
Whirly123
Posts: 31
Joined: Mon May 06, 2019 3:07 pm

Re: Why does a bipolar scale need indifference at zero?

Post by Whirly123 »

Thanks Simonmoon!

Actually this problem was solved (see here: https://forum.cogsci.nl/discussion/8413 ... ion#latest)
Post Reply