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Biomedical subjects

P R Freeman

Publications and source records attributed to P R Freeman.

16 recordsLinked to original sources
PubMed2001

Hypothetical versus real willingness to pay in the health care sector: results from a field experiment.

We conducted a field experiment comparing hypothetical and real purchase decisions for a pharmacist provided asthma management program among 172 subjects with asthma. Subjects received either a dichotomous choice contingent valuation question or were given the opportunity to actually enroll in the program. Three different prices were used: US$ 15, 40, and 80. In the hypothetical group, 38% of subjects said that they would purchase the good at the stated price, but only 12% of subjects in the real group purchased the good (p = 0.000). We cannot, however, reject the null hypothesis that "definitely sure" hypothetical yes responses, as identified in a follow-up question, correspond to real yes responses. We conclude that the dichotomous choice contingent valuation method overestimates willingness to pay, but that it may be possible to correct for this overestimation by sorting out "definitely sure" yes responses.

Adolescent↗
PubMed1997

Sociodemographic and morbidity indicators of need in relation to the use of community health services: observational study.

OBJECTIVE: To examine whether the sociodemographic and morbidity characteristics of populations influence their use of the following community heath services: district nursing, health visiting, chiropody, community maternity, community mental illness, and the professions allied to medicine. DESIGN: Observational study. SETTING: Nationally representative sample of provider trusts in England. MAIN OUTCOME MEASURES: Activity levels for each service calculated for enumeration districts within the catchment areas of the sample of trusts and standardised to allow for differences in age structure. Regression analysis to determine whether the standardised activity rates for each service could be predicted by a range of socio-demographic and morbidity proxies. RESULTS: Morbidity or deprivation, or both, seemed to influence the use of services in each of the care programmes examined. CONCLUSIONS: The allocation of funds for community health services should allow for differences in the health and socio-demographic characteristics of health authorities.

Adolescent↗
PubMed1993

The role of p-values in analysing trial results.

The current widespread practice of using p-values as the main means of assessing and reporting the results of clinical trials cannot be defended. Reasons for grave concern over the present situation range from the unsatisfactory nature of p-values themselves, their very common misunderstanding by statisticians as well as by clinicians and their serious distorting influence on our perception of the very nature of clinical trials. It is argued, however, that only by fully understanding the reasons why they have become so universally popular can we hope to change opinion and introduce more sensible ways of summarizing and reporting results. Some of the ways in which this might happen are discussed.

Bayes Theorem↗
PubMed1989

The performance of the two-stage analysis of two-treatment, two-period crossover trials.

In the two-treatment, two-period crossover trial, patients are randomly allocated either to one group that receives treatment A followed by treatment B, or to another group that receives the treatments in the reverse order. Grizzle first proposed a two-stage procedure for analysing the data from such a trial. This paper examines the long-run sampling properties of this procedure, in terms of mean square error of point estimates, coverage probability of confidence intervals and actual significance level of hypothesis tests for the differences between the effects of the two treatments. The advantages of incorporating baseline observations into the analysis are also explored. Because the preliminary test for carryover is highly correlated with the analysis of data from the first period only, actual significance levels are higher than nominal levels even when there is no differential carryover. When carryover is present, the nominal level very seriously understates the actual level, and this becomes even worse when baseline observations are ignored. Increasing sample size only exacerbates the problem since this adverse behaviour then occurs at smaller values of the carryover effect. It is concluded that the two-stage analysis is too potentially misleading to be of practical use.

Analysis of Variance↗
PubMed1989

A comparison of low-dose maintenance treatment with enprostil against ranitidine in the prevention of duodenal ulcer recurrence.

Enprostil, a prostaglandin E2 analogue, is effective in healing acute duodenal ulcer but its value in preventing recurrence, when given daily for maintenance therapy, is uncertain. In this three-centre study we compared enprostil and ranitidine maintenance therapy; the latter is known to reduce duodenal ulcer relapse rates. Patients whose duodenal ulcers had been healed by treatment with an H2-receptor antagonist were randomized to receive single-blind treatment with either 35 micrograms enprostil (n = 64) or 150 mg ranitidine (n = 64) at bedtime for periods of up to 1 year. Endoscopy was routinely performed at 3 months at one centre, and at 6 and 12 months at all three centres, or whenever ulcer symptoms recurred. Clinical assessment and laboratory investigations were performed every 3 months. Relapse, defined as recurrent ulcer with or without pain, or erosions with pain, was significantly greater in patients on enprostil, the comparative rates at 3, 6 and 12 months were: enprostil 23, 31 and 36% ranitidine 6, 12 and 17% (P = 0.013; P = 0.03 and P = 0.03, respectively). Thirty-one patients reported adverse events, the most common being headache (enprostil = 6, ranitidine = 2) and mild diarrhoea (enprostil = 6, ranitidine = 0). Four patients on enprostil were withdrawn for adverse events, although none terminated because of diarrhoea. There were no clinically significant changes in haematology or biochemistry. Enprostil may reduce duodenal ulcer relapse but at a dose of 35 micrograms nightly, it is less effective than 150 mg ranitidine nightly.

Adult↗
PubMed1982

The effects of methadone on the social behavior and activity of the rat.

Pairs of 80-day-old female rats were given SC injections of either 0, 1, 2.5, or 4 mg/kg of methadone hydrochloride on each of 6 days. Both animals of the pair received the same dose. One hour postinjection, each pair was observed in a circular arena for a five minute period during which the following dependent measures were recorded: total time in contact, latency to initial contact, frequency of aggressive grooms, and locomotor activity. The results indicated that the rats treated with methadone spent less time in contact, took longer to contact, and aggressively groomed each other less frequently than rats treated with a saline vehicle. Also, the results suggested that the disruption of social behavior produced by methadone was not a reflection of decreased activity levels.

Aggression↗
PubMed1980

Methadone exposure in utero: effects on open-field activity in weanling rats.

In a 4 group design, pregnant rats were injected with 0, 4, or 16 mg/kg of methadone hydrochloride daily. The fourth group served as a nonhandled, nontreated control. All females in the first three groups were injected from Day 8 to gestation until term. At birth, litters were weighted, culled to eight pups each, and given to other nontreated surrogate mothers. Daily observation was made to determine infant mortality. At Day 28 of age, offspring were weaned, weighed, and separated by sex. Body weights were low at birth among the high methadone offspring and infant mortality was high. By weaning, mortality remained high, although weights were similar to controls. At weaning, high dose offspring showed depressed open-field activity when compared to low dose and control offspring. Methadone appears to cause deficits in behavioral development which can be detected at weaning.

Animals↗
PubMedDate not supplied

The effects of family history, sobriety length, and drinking history in younger alcoholics on P300 auditory-evoked potentials.

Event-related potentials (ERPs) have been shown to be different between alcoholics and non-alcoholics. Of particular interest to investigators has been the P300 wave. Because it has been shown that alcohol-induced neural damage can alter P300 waves, particularly amplitude, we attempted to examine alcoholics who most likely suffered little damage because they drank heavily for relatively few years (mean = 6.9 years). The effects of long-term sobriety (mean = 5.0) were also investigated to determine if cognitive functioning, as measured by auditory-evoked P300 waves, varies with increased abstinence. Because family history for alcoholism has also been shown to influence P300 amplitude and latency, alcoholics and controls with and without family history were examined. The alcoholic group had significantly longer latencies in P300 measures in both the family history positive and negative groups; P300 amplitudes between alcoholics and non-alcoholics did not vary, regardless of family history. P300 waves were unaffected by sobriety length or drinking history. The results support the hypothesis that P300 differences can be seen between alcoholics and those at risk for alcoholism.

Adult↗