Alternative approaches to multilevel modelling of survey noncontact and refusal

We review three alternative approaches to modelling survey noncontact and refusal: multinomial, sequential and sample selection (bivariate probit) models. We then propose a multilevel extension of the sample selection model to allow for both interviewer effects and dependency between noncontact and refusal rates at the household and interviewer level. All methods are applied and compared in an analysis of household nonresponse in the UK, using a dataset with unusually rich information on both respondents and nonrespondents from six major surveys. After controlling for household characteristics, there is little evidence of residual correlation between the unobserved characteristics affecting noncontact and refusal propensities at either the household or the interviewer level. We also find that the estimated coefficients of the multinomial and sequential models are surprisingly similar, which further investigation via a simulation study suggests is due to there being little overlap between the predictors of noncontact and refusal

Multilevel modelling of refusal and noncontact nonresponse in household surveys: evidence from six UK government surveys

This paper analyses household unit nonresponse and interviewer effects in six major UK government surveys using a multilevel multinomial modelling approach. The models are guided by current conceptual frameworks and theories of survey participation. One key feature of the analysis is the investigation of survey dependent and independent effects of household and interviewer characteristics, providing an empirical exploration of the leverage-salience theory. The analysis is based on the 2001 UK Census Link Study, a unique data source containing an unusually rich set of auxiliary variables, linking the response outcome of six surveys to census data, interviewer observation data and interviewer information, available for respondents and nonrespondents

Contraceptive confidence and timing of first birth in Moldova: an event history analysis of retrospective data

Objectives: To test the contraceptive confidence hypothesis in a modern context. The hypothesis is that women using effective or modern contraceptive methods have increased contraceptive confidence and hence a shorter interval between marriage and first birth than users of ineffective or traditional methods. We extend the hypothesis to incorporate the role of abortion, arguing that it acts as a substitute for contraception in the study context.Setting: Moldova, a country in South-East Europe. Moldova exhibits high use of traditional contraceptive methods and abortion compared with other European countries.Participants: Data are from a secondary analysis of the 2005 Moldovan Demographic and Health Survey, a nationally representative sample survey. 5377 unmarried women were selected.Primary and secondary outcome measures: The outcome measure was the interval between marriage and first birth. This was modelled using a piecewise-constant hazard regression, with abortion and contraceptive method types as primary variables along with relevant sociodemographic controls.Results: Women with high contraceptive confidence (modern method users) have a higher cumulative hazard of first birth 36?months following marriage (0.88 (0.87 to 0.89)) compared with women with low contraceptive confidence (traditional method users, cumulative hazard: 0.85 (0.84 to 0.85)). This is consistent with the contraceptive confidence hypothesis. There is a higher cumulative hazard of first birth among women with low (0.80 (0.79 to 0.80)) and moderate abortion propensities (0.76 (0.75 to 0.77)) than women with no abortion propensity (0.73 (0.72 to 0.74)) 24?months after marriage.Conclusions: Effective contraceptive use tends to increase contraceptive confidence and is associated with a shorter interval between marriage and first birth. Increased use of abortion also tends to increase contraceptive confidence and shorten birth duration, although this effect is non-linear—women with a very high use of abortion tend to have lengthy intervals between marriage and first birth

The Lawyer as Peacemaker

This J. Reuben Clark Law School convocation address was given at the Provo Tabernacle on April 25, 2008

The Lawyer as Peacemaker

This J. Reuben Clark Law School convocation address was given at the Provo Tabernacle on April 25, 2008

The correlates of natural method use in Moldova: is natural method use associated with poverty and isolation?

Natural method use is often associated with high levels of unwanted births and induced abortions. This study investigates the correlates of natural method use in Moldova, a country with one of the highest proportions of natural contraceptive users in Europe. We hypothesize that economic and spatial disadvantage increase the reliance on natural methods whereas exposure to FP programs decreases the probability of natural method use. The analysis considers a sub-sample of 5860 sexually-active women from the 2005 Demographic and Health Survey. Results from multilevel multinomial models, controlling for relevant characteristics and data structure, show that economic disadvantage increases the probability of natural method use; but the overall effect is small. Higher FP media exposure reduces natural method use; however this effect attenuates with age. We conclude that FP efforts directed towards the poorest may have limited impact, but interventions targeted at older women could reduce the burden of unwanted pregnancies

Inertial navigation systems for mobile robots

Cataloged from PDF version of article.A low-cost solid-state inertial navigation system (INS) for mobile robotics applications is described. Error models for the inertial sensors are generated and included in an Extended Kalman Filter (EKF) for estimating the position and orientation of a moving robot vehicle. Two Merent solid-state gyroscopes have been evaluated for estimating the orientation of the robot. Performance of the gyroscopes with error models is compared to the performance when the error models are excluded from the system. The results demonstrate that without error compensation, the error in orientation is between 5-15"/min but can be improved at least by a factor of 5 if an adequate error model is supplied. Siar error models have been developed for each axis of a solid-state triaxial accelerometer and for a conducting-bubble tilt sensor which may also be used as a low-cost accelerometer. Linear position estimation with information from accelerometers and tilt sensors is more susceptible to errors due to the double integration process involved in estimating position. With the system described here, the position drift rate is 1-8 cds, depending on the frequency of acceleration changes. An integrated inertial platform consisting of three gyroscopes, a triaxial accelerometer and two tilt sensors is described. Results from tests of this platform on a large outdoor mobile robot system are described and compared to the results obtained from the robot's own radar-based guidance system. Like all inertial systems, the platform requires additional information from some absolute position-sensing mechanism to overcome long-term drift. However, the results show that with careful and detailed modeling of error sources, low-cost inertial sensing systems can provide valuable orientation and position information particularly for outdoor mobile robot applications

Extended conjugated microporous polymers for photocatalytic hydrogen evolution from water

Conjugated microporous polymers (CMPs) have been used as photocatalysts for hydrogen production from water in the presence of a sacrificial electron donor. The relative importance of the linker geometry, the co-monomer linker length, and the degree of planarisation were studied with respect to the photocatalytic hydrogen evolution rate

Evaluation of solid-state gyroscope for robotics applications

Cataloged from PDF version of article.he evaluation of a low-cost solid-state gyroscope for robotics applications is described. An error model for the sensor is generated and included in a Kalman filter for estimating the orientation of a moving robot vehicle. Orientation eshation with the error model is compared to the performance when the error model is excluded from the system. The results demonstrate that without error compensation, the error in localization is between 5-15"/min but can be improved at least by a factor of 5 if an adequate error model is supplied. Like all inertial systems, the platform requires additional information from some absolute position-sensing mechanism to overcome long-term drift. However, the results show that with careful and detailed modeling of error sources, inertial sensors can provide valuable orientation information for mobile robot applications

Catalyst-Switchable Regiocontrol in the Direct Arylation of Remote C—H Groups in Pyrazolo[1,5-<i>a</i>]pyrimidines

The regiodivergent palladium-catalyzed C–H arylation of pyrazolo[1,5-a]pyrimidine has been achieved, wherein the switch in regioselectivity between positions C3 and C7 is under complete catalyst control. A phosphine-containing palladium catalyst promotes the direct arylation at the most acidic position (C7), whereas a phosphine-free catalyst targets the most electron-rich position (C3)