PubMed Health⌕ Search

PubMed · 11084228

Proportion estimation with confidence limits.

Abstract

A common task in microbiology involves determining the composition of a mixed population of individuals by drawing a sample from the population and using some procedure to identify the individuals in the sample. There may be a significant probability that the identification procedure misidentifies some members of the sample (for example, because the available data are insufficient unambiguously to identify an individual) which makes finding the proportions in the underlying population non-trivial. A further complication arises where individuals are present in the population that do not belong to any of the subpopulations recognised by use of the identification procedure. A simple algorithm is presented to address these problems and construct a maximum likelihood estimate of the proportions, together with confidence limits. The technique is illustrated using an example drawn from flow cytometry in which phytoplankton cells are identified from flow cytometry data by an RBF neural network, and the limitations of the approach are discussed.

Explore related subjects

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

M F Wilkins, L Boddy, C W Morris. 2000-12-01. Proportion estimation with confidence limits.. https://doi.org/10.1016/s0167-7012(00)00204-9

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

Elbow impedance during goal-directed movements.

The mechanical properties and reflex actions of muscles crossing the elbow joint were examined during a 60-deg voluntary elbow extension movement. Brief unexpected torque pulses of identical magnitude and time-course (20-Nm extension switching to 20-Nm flexion within 30 ms) were introduced at various points of a movement in randomly selected trials. Single pulses were injected in different trials, some before movement onset and some either during early, mid, late or ending stages of the movement. Changes in movement trajectory induced by a torque pulse were determined over the first 50 ms by a nearest-neighbor prediction algorithm, and then a modified K-B-I (stiffness-damping-inertia) model was fit to the responses. The stiffness and damping coefficients estimated during voluntary movements were compared to values recorded during trials in which subjects were instructed to strongly co-contract while maintaining a static posture. This latter protocol was designed to help determine the maximum impedance a subject could generate. We determined that co-contraction increased joint stiffness greatly, well beyond that recorded under control conditions. In contrast, the stiffness magnitudes were quite small during routine voluntary movements, or when the subjects relaxed their limb. Furthermore, the damping coefficients were always significant and increased measurably at the end of movement. Reflex activity, as measured by EMG responses in biceps and triceps brachii, showed highly variable responses at latencies of 160 ms or greater. These reflexes tended to activate both elbow flexors and extensors simultaneously. These findings suggest that very low intrinsic muscle stiffness values recorded during point-to-point motion render an equilibrium point or impedance control approach implausible as a means to regulate movement trajectories. In particular, muscle that is shortening against inertial loads seems to exhibit much smaller stiffness than similarly active isometric muscle, although some degree of damping is always present and does not simply co-vary with stiffness. Although the limb muscles can be co-contracted statically or during movement with an observable increase in stiffness and even task performance, this control strategy is rarely utilized, presumably due to the greater energetic cost.

Confidence Intervals↗

Assessment of whether in-hospital mortality for lobectomy is a useful standard for the quality of lung cancer surgery: retrospective study.

OBJECTIVES: To calculate in-hospital mortality after lobectomy for primary lung cancer in the United Kingdom; to explore the validity of using such data to assess the quality of UK thoracic surgeons; and to investigate the relation between in-hospital mortality and the number of procedures performed by surgeons. DESIGN: Retrospective study. SETTING: 36 departments dealing with thoracic surgery in UK hospitals. PARTICIPANTS: 4028 patients who had undergone lobectomy for primary lung cancer by one of 102 surgeons. MAIN OUTCOME MEASURES: In-hospital mortality in relation to individual surgeons, among all patients, and among each of five groups of patients defined by the number of operations performed by the surgeon. RESULTS: 103 patients (2.6%, 95% confidence interval 2.1% to 3.1%) died after surgery during the same hospital admission. No significant difference was found for in-hospital mortality between the five groups. CONCLUSIONS: The number of procedures performed by a thoracic surgeon is not related to in-hospital mortality. Reporting data on in-hospital mortality after lobectomy for primary lung cancer is a poor tool for measuring a surgeon's performance.

Confidence Intervals↗