Hi,
I am most grateful for all the knowledge you people dispense on statalist. I
have learnt a lot through it.
I have two problems:
1) The first one concerns the effect of two different interventions:
At baseline, 20 % of patients admitted with disease X at Hospital 1 were
cured
At baseline, 30 % of patients admitted with disease X at Hospital 2 were
cured
Training 1 was given to doctors in Hospital 1
Training 2 was given to doctors in Hospital 2
In the Post-intervention period:
60 % of patients admitted to Hospital 1 were cured
55 % of patients admitted to Hospital 2 were cured
Obviously, Training 1 seems to work better than Training 2.
O How can it be shown that this "difference in improvement in cure rates" is
statistically significant? i.e. one training is better than the other?
(Note: This is NOT paired data.. the patients are different)
s Can a sample size be calculated for this situation?
I know its not a perfect study, but given the current situation, what can be
done?
The best I was able to do was to calculate the 95 % CI for the improvement
in cure for hospital 1, then calculate the 95 % CI for improvement in cure
for hospital 2. The CIs overlapped, indicating that the "improvement in cure
rates" were not statistically different.
2) Comparing Z-score distribution in a study group with mental difficulties
against the normal population:
Scores on a cognitive test were measured in a group of students drawn from
an institution for the mentally challenged.
z-scores were calculated for these cognitive scores using means and SD for
this test in the general population.
A person had a z-score of lesser than -2 (i.e. was below 2 SD on the curve
for normal individuals) was considered to be "Cognitively deficient"
A person with a z-score of -2 to -1 was labeled as "Borderline Cognitive
functioning"
Say the scores in the study group were as follows:
Normal (>-1SD) 50 % (8/16)
Borderline (-1SD to -2SD) 25 % (4/16)
Deficient (below -2 SD) 25 % (4/16)
These values are obviously abnormal. The values expected based on the
z-score distribution for normal people are: 84 %, 13.5 % and 2.5 %
respectively.
What is the best way to show that the distribution of Z-scores in the
mentally challenged children was abnormal? What statistical test can be
performed?
I was thinking in terms of making another column "NUMBER of people expected
if the distribution was normal, given a sample size of 16" and then doing a
chi2 on the observed v/s expected categories.
The problem is that the "Number of expected people" will be a decimal number
e.g. 2.5/100 x 16 = 0.4. which doesn't make much sense..
A big THANK YOU for any replies that follow. I have been a keen follower of
statalist and cant thank you guys enough for all that I have learnt through
it.
Thanks and regards,
Siddharth Kharkar.
*
* For searches and help try:
* http://www.stata.com/support/faqs/res/findit.html
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/
