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So I am a med student writing up results for a research project which was conducted in the form of a survey. I have no prior training with stats so I am very much struggling, I have collected all data, run a few tests but upon further reading, I am wondering whether the tests I did are appropriate or not. I know there's differences of opinion in the stats worlds as to which test is the best and that might be why I am having doubts.

In this question I will inlcude real numbers but the questions will be different in order to keep my topic private.

1) How would you classify your medical condition? Acute? Chronic? or Don't Know?
2) How would you rate being called by your first name by doctors? (Likert item) Strongly dislike , dislike, neutral, like, Strongly like

In my analysis I want to see whether the condition being acute or chronic has any association with the opinion of patients on the likert scale (q2) so I made this table

enter image description here

I ran a chi-square test on this website (https://www.socscistatistics.com/tests/chisquare2/default2.aspx) and got chi value as 9.0368 and p=.34 (no significant association)

OK SO my questions:
1) Is this test appropriate for this data? If it's not the best is it still valid? By valid I mean can it still be used to make a point in a paper, I'm not concerned with finesse and using the best possible test (although I am interested), I care more about not using the wrong test which is completely inapproariate for the data
2) I read somewhere that chi square isn't appropriate for ordinal data like mine? How true is this?
3) If the test yielded a significant result p less than .05, how would i describe the association? Would I just go by percentages for example: For acute conditions 40% of patients said the strongly liked being called by xxx whereas for those with chronic conditions only 20% strongly liked to be called by xxx? This is very confusing for me because even for some of the other data similar to this in format I get significant results but I have no idea how to describe it.
4) Does anything change for data where there is only 2 rows for example if there was only (acute/chronic, without Don't know)?

Thanks!!!

1 Answers1

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I put your table into R and ran a chi-squared test of homogeneity, which gave the same results as in your question. If this test had rejected the null hypothesis, then you would have evidence that profiles of Likert scores across categories A, C, D are significantly different. Also, you would have the job of seeing which Likert scores accounted for the difference(s) among categories.

You are correct that this chi-squared test ignores the ordinal aspect of the Likert data. A controversial alternative is to treat Likert scores as if they are numerical, so that it makes sense to add and average them.

Pretending that Likert scores are numerical (and not far from normal) would lead to a one-way ANOVA with three levels A, C, D of the factor. We are treating Likert categories as if they corresponded to numbers 1 through 5.

Here is how to run such an ANOVA in R.

a = c(10,12,25,8,7)
c = c(10,14,58,22,15)
d = c(7,5,24,14,4)
x1 = rep(1:5, a)
x2 = rep(1:5, c)
x3 = rep(1:5, d)
x = c(x1,x2,x3)
g = rep(1:3, c(62, 119, 54))
oneway.test(x ~ g)

        One-way analysis of means 
     (not assuming equal variances)

data:  x and g
F = 1.5024, num df = 2.00, 
   denom df = 117.44, p-value = 0.2268

Controversial or not, this test shows no significant differences in the averages of A, C, D categories. The Likert responses in the three groups are too similar to use them to say anything about categories.

Average Likert scores and standard deviations at the three levels are as follows:

mean(x1); mean(x2); mean(x3)
[1] 2.83871
[1] 3.151261
[1] 3.055556
sd(x1); sd(x2); sd(x3)
[1] 1.190034
[1] 1.062765
[1] 1.088823

One difficulty trying to find differences among A, C, D groups is that all groups had very high proportions of 'Neutral' choices among the five Likert responses.

BruceET
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  • Thank you for your kind response, you mentioned turning the likert scale into numbers is controversial, how controversial is this ocnsidering a likert scale is supposed to represent answers of about equal interval? Also since the chi square test ignores the ordinal likert scale, from a pratical point of view how useful is this analysis? Is it completely inappropriate or is is just not the best one that can be done? Lastly if I only have A and C no D variable can I then use the Mann Whitney U test? Can I still use the ANOVA? Which onw would be more appropriate? – Chaudry Shahid Iqbal Jun 03 '20 at 08:48
  • https://www.socscistatistics.com/tests/anova/default2.aspx Is this website good enough to do ANOVA tests? – Chaudry Shahid Iqbal Jun 03 '20 at 08:48
  • From the first paragraph of your answer I understand that the chi square test will still detect differences but I guess wouldn;t consider the spread of the data? i.e. if it's more towards SA/A or SD/D Thanks – Chaudry Shahid Iqbal Jun 03 '20 at 08:50
  • Also the ANOVA test assumes normal distribution right? Wouldn't a Kruskal-Wallis test be more approriate? – Chaudry Shahid Iqbal Jun 03 '20 at 09:25
  • KW would be OK. In fact, I tried it. Results effectively same as for my Satterthwaite ANOVA. (Didn't show it; didn't want give impression of P-hacking, looking for signif result.) Your smallest group has 54. Likert scores are not normal, but they are bounded (so no outliers), and yours are roughly symmetrical. Issue is not whether observations are nearly normal, but whether sample means are. You have only three of them so formal test impossible. However, re-sampling means of 50 from Likert data shows means can be taken as normal. – BruceET Jun 03 '20 at 15:43
  • Right makes sense.... would it be possible to avoid all this and use chi square with this test having some usefulness? It's not completely useless is it? I guess with KW you get more info since you can evaluate spread? Isn't there a difference of opinion re whether likert is ordinal or nominal anyway? Thanks – Chaudry Shahid Iqbal Jun 03 '20 at 19:13
  • It would be OK to treat Likert data as ordinal and do a a chi-squared test of homogeneity of Likert categries across A,C,D. It might be best to recognize Likert responses as ordinal and do a K-W test. Although controversial, you might get useful information treating Likert scores as if they were interval numerical and do an ANOVA. // But with your data this discussion is not very productive, because the Likert scores are very much the same for A,C,D and you won't get significant results with any of these methods. – BruceET Jun 03 '20 at 19:37