| 1. |
- Chotai, Jayanti, 1948-
(författare)
-
Likelihood ratio procedures for subset selection and ranking problems
- 1979
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report deals with procedures for random-size subset selection fromk(> 2) given populations where the distribution of ir^(i = l, ..., k)has a density f^(x;0^). Let ••• -®[k] denote unknown values ofthe parameters, and let ^[i]» ***'ïï[k] denote the corresponding populations.First, we have considered the problem of selection for consider the/sprocedure that selects TT. if sup L(0;x) > c L(0;x), where L(*;x) is the1 e e u . - - - - -itotal likelihood function, where is the region m the parameter space foriA9= (0^, ..., 0^) having 0^ as the largest component, where 9 is the maximum likelihood estimate of 0 , and where c is a given constant with 0 < c < l .With the densities satisfying seme reasonable requirements given in this report,we have shown that for each i, the probability of includingthe selected subset is decreasing in ®[j] f°r j t i anc* increasing inWe have then derived some results on selection for the t(> 1) best populations,thereby generalizing the results for t = 1. For this problem, we haveconsidered a) selection of a set whose elements consist of subsets of thegiven populations having t members, and requiring that the set of the t• » • • •best populations is included with probability at least P , b) selection ofa subset of the populations so as to include all the t best populationswith probability at least P'*, and c) selection of a subset of the populationssuch that TT[j ^ is included with probability at least P*, j=k-t+l,.•., k. In the final section, we have discussed the relation between thetheories of subset selection based on likelihood ratios and statistical inferenceunder order restrictions, and have considered the complete rankingproblem.
|
|
| 2. |
- Chotai, Jayanti, 1948-
(författare)
-
Season of birth in suicidology : neurobiological and epidemiological studies
- 1999
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Several neuropsychiatrie disorders have shown season of birth associations. Low cerebrospinal fluid (CSF) levels of the serotonin metabolite 5-HIAA and the dopamine metabolite HVA have been associated with suicidal behaviour, impulsivity, and aggression. This thesis investigated associations between the season of birth, the CSF levels of three monoamine metabolites (including MHPG of norepinephrine), the scales of the diagnostic interview for borderline patients (DIB), and psychiatric diagnoses. Also, the methods of suicide were investigated in relation to the season of birth.Methods: We studied a clinical sample of 241 patients in Stockholm with mood, anxiety and adjustment disorders with respect to the CSF levels of monoamine metabolites in relation to the season of birth, and in relation to the DIB in an overlapping sample. We also analysed all completed suicides during the 42 years 1952- 1993inVästerbottenin northern Sweden (1466 cases) by multiple logistic regressions to relate suicide methods with season of birth, gender, age, urban-rural residence, marital status, year of suicide, and season of suicide. For the 20 years 1961- 1980 (693cases), psychiatric in-patient and out-patient records were also examined for any history of psychiatric contacts and psychiatric diagnoses. In two mutually independent samples, we investigated the DIB in relation to the season of birth.Results: In the Stockholm sample, those born during February to April had significantly lower CSF levels of 5-HIAA, and those born during October to January had significantly higher CSF levels of HVA, HVA/5-HIAA, and HVA/MHPG, as well as (non-significantly) higher levels of 5-HIAA. Those with an intermediate score of section II (impulse action patterns) of the DIB had significantly higher CSF levels of 5-HIAA and HVA, and they were significantly more likely to have been born during October to January. In the Västerbotten register, those born during February to April were significantly more likely to have preferred hanging rather than poisoning or petrol gases, and conversely for those born during October to January. These associations with suicide methods were found for the total sample and for those without any history of psychiatric contacts, but not for those with psychiatric contacts.Conclusions: Suicidal behaviour shows statistically significant variation according to the season of birth, most probably mediated by a variation in an independent trait of vulnerability to suicide based on neurodevelopmental parameters, particularly the serotonergic system. The suicidal process differs between those who seek psychiatric care compared to those who do not, reflecting differences in the diagnostic spectra and in the extent of mental illness.
|
|
| 3. |
- Chotai, Jayanti, 1948-
(författare)
-
Selection and ranking procedures based on likelihood ratios
- 1979
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with random-size subset selection and ranking procedures• • • )|(derived through likelihood ratios, mainly in terms of the P -approach.Let IT , . .. , IT, be k(> 2) populations such that IR.(i = l, . . . , k) hasJ_ K. — 12the normal distribution with unknwon mean 0. and variance a.a , where a.i i i2 . . is known and a may be unknown; and that a random sample of size n^ istaken from . To begin with, we give procedure (with tables) whichselects IT. if sup L(0;x) >c SUD L(0;X), where SÎ is the parameter space1for 0 = (0-^, 0^) ; where (with c: ß) is the set of all 0 with0. = max 0.; where L(*;x) is the likelihood function based on the total1sample; and where c is the largest constant that makes the rule satisfy theP*-condition. Then, we consider other likelihood ratios, with intuitivelyreasonable subspaces of ß, and derive several new rules. Comparisons amongsome of these rules and rule R of Gupta (1956, 1965) are made using differentcriteria; numerical for k=3, and a Monte-Carlo study for k=10.For the case when the populations have the uniform (0,0^) distributions,and we have unequal sample sizes, we consider selection for the populationwith min 0.. Comparisons with Barr and Rizvi (1966) are made. Generalizai
|
|
| 4. |
- Chotai, Jayanti, 1948-
(författare)
-
Subset selection based on likelihood from uniform and related populations
- 1979
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Let π1, π2, ... π be k (>_2) populations. Let πi (i = 1, 2, ..., k) be characterized by the uniform distributionon (ai, bi), where exactly one of ai and bi is unknown. With unequal sample sizes, suppose that we wish to select arandom-size subset of the populations containing the one withthe smallest value of 0i = bi - ai. Rule Ri selects πi iff a likelihood-based k-dimensional confidence region for the unknown (01,..., 0k) contains at least one point having 0i as its smallest component. A second rule, R, is derived through a likelihood ratio and is equivalent to that of Barr and Rizvi (1966) when the sample sizes are equal. Numerical comparisons are made. The results apply to the larger class of densities g(z; 0i) = M(z)Q(0i) iff a(0i) < z < b(0i). Extensions to the cases when both ai and bi are unknown and when 0max is of interest are i i indicated.
|
|
| 5. |
- Chotai, Jayanti, 1948-
(författare)
-
Subset selection based on likelihood ratios : the normal means case
- 1979
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Let π1, ..., πk be k(>_2) populations such that πi, i = 1, 2, ..., k, is characterized by the normal distribution with unknown mean and ui variance aio2 , where ai is known and o2 may be unknown. Suppose that on the basis of independent samples of size ni from π (i=1,2,...,k), we are interested in selecting a random-size subset of the given populations which hopefully contains the population with the largest mean.Based on likelihood ratios, several new procedures for this problem are derived in this report. Some of these procedures are compared with the classical procedure of Gupta (1956,1965) and are shown to be better in certain respects.
|
|
| 6. |
- Chotai, Jayanti, 1948-
(författare)
-
Suicide, personality and neurodevelopment
- 2012
-
Ingår i: Suicide from a global perspective. - : Nova Science Publishers, Inc.. - 9781619422674 - 9781619422797 ; , s. 97-102
-
Bokkapitel (refereegranskat)
|
|
| 7. |
- Hansson, Maja, 1980-, et al.
(författare)
-
What made me feel better? : patients' own explanations for the improvement of their depression
- 2012
-
Ingår i: Nordic Journal of Psychiatry. - : Taylor & Francis. - 0803-9488 .- 1502-4725. ; 66:4, s. 290-296
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Depression is common among primary care patients and the usual treatment often consists of antidepressant medication and supportive counselling/follow-ups. Previous studies have shown that patients and professionals have different beliefs about treatment, which in turn can decrease acceptance of the diagnosis, compliance and treatment outcome.Aims: The purpose of this study was to investigate previously depressed patients’ beliefs about the cause of their improvement. Methods: Depressed primary care patients (n = 184) who considered themselves improved at follow-up answered an open-ended question about what they believed had made them better. Among these 117 patients had, in addition to treatment as usual, participated in an intervention with patient education and group counselling (the Contactus programme), whereas 67 were controls. The groups were comparable at baseline and 82% were on antidepressants. Results: In total, the patients mentioned 14 separate improving factors, which could be organized to the larger themes external factors, self-management, passing spontaneously and professional help. The most frequently mentioned factors for improvement were the Contactus programme (53.0%), antidepressants (40.2%) and personal development (27.2%). Few gender and age differences were seen. The controls who mentioned professional help were more likely to have a better outcome. Conclusions: The patients were generally positive to professional help such as antidepressants and the Contactus programme. Patient education and group counselling seems to be a valuable supplement to treatment of depressed patients in primary care.
|
|
