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Proc Means confidence limit gives "."

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Occasional Contributor ST1
Occasional Contributor
Posts: 5

Proc Means confidence limit gives "."

[ Edited ]

Hi Everyone,

I am trying to get the 95% confidence interval for a disease severity progression data set in SAS 9.4. The data have been log transformed and are not normal (certain weeks have a lot of 0 values).  Sometimes the confidence limit output contains "." rather than numbers. In the year 2 output it seems that this only happens when the disease severy mean in 0 (see year 2 below), but in the year 1 data it happens for weeks when the disease severity mean is 0.3010 or 0 (see year 1 below).  My question is: what does the "." mean? Why is a "." returned even when the mean is not 0?

Thank you

Sherri Smiley Happy

 

This is the coding for year 2:

Title2 "Confidence Interval";
proc means data= first maxdec=4 alpha=0.05 clm mean;
class trt;
var jul23 jul31 aug6 aug13 aug20 aug27 sep3 sep10 sep17;
run;

 

and this is part of the output: 

year2.png

 

Coding for year 1

Title2 "Confidence Interval";
proc means data= first maxdec=4 alpha=0.05 clm mean;
class trt;
var aug21 aug30 sep14 sep24 oct11;
run;

 

Output for year 1:

year1.png

Super User
Posts: 5,085

Re: Proc Means confidence limit gives "."

Is it possible you have missing values in your data?  If only one observation has a nonmissing value, you can get a mean.  But you can't get confidence limits.  Perhaps you could check your data for a few of these cases.

Occasional Contributor ST1
Occasional Contributor
Posts: 5

Re: Proc Means confidence limit gives "."

[ Edited ]

There are 3 missing values in the year 1 data set (Oct 11 trt 2, and Sept 24 and Oct 11 trt 3), but they don't seem to correspond to the missing values in the confidence limit output. If it helps provide context, both data sets have 7 trt and four reps

Super User
Posts: 5,085

Re: Proc Means confidence limit gives "."

Perhaps you could share some of the data.  There are other conditions where there would be a mean but no confidence limit, such as all values being identical.  Are you able to share all the data points for one set of values that has no confidence limits?

Occasional Contributor ST1
Occasional Contributor
Posts: 5

Re: Proc Means confidence limit gives "."

Here is data for trt 7 of year 1 

block trt  aug21 aug30 sep14 sep24 oct11;
1	7	0	0	0.2	0.5	1
2	7	0	0	0	0.6	1
3	7	0	0.1	0	0.9	1
4	7	0	0	0	0.5	1
;
Super User
Posts: 17,870

Re: Proc Means confidence limit gives "."

Add Standard Deviation to the chart please and repost. 

Occasional Contributor ST1
Occasional Contributor
Posts: 5

Re: Proc Means confidence limit gives "."

Please see orginal message for update chart.

Super User
Posts: 17,870

Re: Proc Means confidence limit gives "."

Do you see the issue? Smiley Happy

 

All results with missing CI have a standard deviation of 0 - implying that the values are all that single value.

Super User
Posts: 9,687

Re: Proc Means confidence limit gives "."

As Reeza pointed out . You can not calculated CI when it is at the highest level (nway), there is only one obs for that. Specify WAYS statement.
proc means data= first maxdec=4 alpha=0.05 clm mean;
class trt;
ways 1 ;
var jul23 jul31 aug6 aug13 aug20 aug27 sep3 sep10 sep17;
run;
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