Active Learning with Statistical Models

D. CohnZoubin GhahramaniMichael I. Jordan

article1996NeurIPS2,574 citations

Derives exact, closed-form criteria for active data selection through variance minimization in mixtures of Gaussians and locally weighted regression, enabling computationally efficient query selection that drastically reduces the training examples required for accurate regression.

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The article addresses the challenge of efficiently acquiring training data for machine learning systems when each data point is costly or time-consuming to obtain, as is common in industrial or robotic applications. Passive approaches that rely on random or fixed data collection waste resources by including uninformative examples, whereas active learning lets the system select the most useful inputs to query. This matters now because many real-world tasks, such as robot control or sensor placement, involve high expenses per measurement and could benefit from drastic reductions in required data.

The article sets out to demonstrate that statistically optimal data selection, previously applied approximately and expensively to neural networks, can be performed efficiently and accurately with two alternative statistical models: mixtures of Gaussians and locally weighted regression. It derives closed-form criteria for choosing queries that minimize the learner's expected variance and tests them empirically.

The approach combines theoretical analysis with controlled experiments on a two-degree-of-freedom robot arm kinematics task. The models estimate output variance after a candidate query, integrate that expectation over a reference set drawn from the known input distribution, and select the query that yields the lowest average variance. Performance is compared against random sampling on learning curves for both estimated variance and mean squared error, using training sets up to several hundred examples and multiple runs with added input noise.

The key findings are that the variance-minimizing criterion produces learning curves with substantially lower error than random selection; for mixtures of Gaussians the mean squared error is consistently about one-third that of the random baseline, while locally weighted regression shows even larger gains and outperforms both mixtures and prior neural-network results. Computation times remain practical, scaling linearly with training-set size for mixtures and remaining fast enough for many control tasks with locally weighted regression. The optimality criterion sharply reduces the number of examples needed to reach good performance.

These results imply that organizations facing expensive data collection can achieve equivalent model accuracy with far fewer measurements, yielding major savings in time and cost while maintaining statistical grounding. The methods also produce parsimonious training sets that speed up subsequent predictions.

Next steps supported by the article include extending the framework to minimize bias as well as variance, deriving similar criteria for Bayesian networks and classification models, and testing on additional domains. Further work is needed to handle cases where the learner's bias is non-negligible and to incorporate regularization or convergence detection during fitting.

Limitations include the assumption that learners are approximately unbiased and that noise is roughly Gaussian; results are reported for a single low-dimensional task; and the input distribution must be known or approximable. Confidence is high for the tested conditions and models, but readers should be cautious about generalizing to high-bias settings or very high-dimensional problems without additional validation.

  • Paper: Query by committee, H. Seung et al. (1992). This foundational paper establishes the query-by-committee paradigm for active learning using model disagreement, motivating the statistical and variance-reduction criteria developed in the source.
  • Paper: Neural Network Ensembles, Cross Validation, and Active Learning, Anders Krogh et al. (1994). It formulates active data selection based on ensemble ambiguity and variance, providing theoretical foundations for variance-minimizing query selection in statistical models.
  • Paper: Hierarchical Mixtures of Experts and the EM Algorithm, Michael I. Jordan et al. (1994). It introduces hierarchical mixtures of experts and their estimation via EM, establishing the mixture model architecture that the source adapts for closed-form active learning.
  • Paper: Adaptive Mixtures of Local Experts, Robert A. Jacobs et al. (1991). It presents the adaptive mixture of local experts framework used as a primary statistical architecture in the source's data selection experiments.
Cover for Active Learning with Statistical Models

Abstract

For many types of machine learning algorithms, one can compute the statisticallyoptimalway to select training data. In this paper, we review how optimal data selection techniques have been used with feedforward neural networks. We then show how the same principles may be used to select data for two alternative, statistically-based learning architectures: mixtures of Gaussians and locally weighted regression. While the techniques for neural networks are computationally expensive and approximate, the techniques for mixtures of Gaussians and locally weighted regression are both efficient and accurate. Empirically, we observe that the optimality criterion sharply decreases the number of training examples the learner needs in order to achieve good performance.

Table of Contents

  • 1. Introduction
  • 2. Active Learning – A Statistical Approach
  • 2.1 Selecting Data to Minimize Learner Variance
  • 2.2 Example: Active Learning with a Neural Network
  • 3. Mixtures of Gaussians
  • 3.1 Active Learning with a Mixture of Gaussians
  • 4. Locally Weighted Regression
  • 4.1 Setting the Smoothing Parameter k
  • 4.2 Active Learning with Locally Weighted Regression
  • 5. Experimental Results
  • 5.1 Experiments with Mixtures of Gaussians
  • 5.2 Experiments with LOESS Regression
  • 5.3 Computation Time
  • 6. Discussion
  • Appendix A. Notation
  • Acknowledgements
  • References

Knowls

  1. Knowl 1 — Variance-Minimization Objective for Supervised Active Learning

    theoretical result

    In supervised active learning, the expected mean squared error of a learner's prediction y^(x;D)\hat{y}(x; \mathcal{D}) given a training set D\mathcal{D} relative to the true target y(x)y(x), integrated over the marginal input distribution P(x)P(x), decomposes as:

    XET[(y^(x;D)y(x))2x]P(x)dx=X(E[(y(x)E[yx])2]+(ED[y^(x;D)]E[yx])2+ED[(y^(x;D)ED[y^(x;D)])2])P(x)dx\int_X E_{\mathcal{T}}\left[(\hat{y}(x; \mathcal{D}) - y(x))^2 \mid x\right] P(x) \, dx = \int_X \left( E\left[(y(x) - E[y \mid x])^2\right] + (E_{\mathcal{D}}[\hat{y}(x; \mathcal{D})] - E[y \mid x])^2 + E_{\mathcal{D}}\left[(\hat{y}(x; \mathcal{D}) - E_{\mathcal{D}}[\hat{y}(x; \mathcal{D})])^2\right] \right) P(x) \, dx

    where ET[]E_{\mathcal{T}}[\cdot] denotes expectation over P(yx)P(y \mid x) and training sets D\mathcal{D}, while ED[]E_{\mathcal{D}}[\cdot] denotes expectation over training sets D\mathcal{D} with fixed input components. The first term is the noise variance of the output, the second is the learner's squared bias, and the third is the learner's prediction variance σy^2(x)\sigma_{\hat{y}}^2(x).

    Under the assumption that the learning model is approximately unbiased (squared bias is negligible compared to variance), active data selection minimizes expected future error by selecting a query input x~\tilde{x} that minimizes the expected integrated learner variance:

    Xσ~y^2(x)P(x)dx\int_X \langle \tilde{\sigma}_{\hat{y}}^2(x) \rangle P(x) \, dx

    where σ~y^2(x)=ED{(x~,y~)}[σy^x~2(x)]\langle \tilde{\sigma}_{\hat{y}}^2(x) \rangle = E_{\mathcal{D} \cup \{(\tilde{x}, \tilde{y})\}}\left[ \sigma_{\hat{y} \mid \tilde{x}}^2(x) \right] is the expected variance at xx after incorporating query (x~,y~)(\tilde{x}, \tilde{y}), with expectation evaluated over the conditional output distribution P(y~x~)P(\tilde{y} \mid \tilde{x}).

  2. Knowl 2 — Prediction and Output Variance in Gaussian Mixture Regression

    model/method

    A Mixture of Gaussians models the joint density on the input-output space X×YX \times Y using NN multivariate Gaussian components gig_i parameterized by means μi=[μx,i,μy,i]T\mu_i = [\mu_{x,i}, \mu_{y,i}]^T and covariances Σi=[σx,i2σxy,iσxy,iσy,i2]\Sigma_i = \begin{bmatrix} \sigma_{x,i}^2 & \sigma_{xy,i} \\ \sigma_{xy,i} & \sigma_{y,i}^2 \end{bmatrix}.

    For an arbitrary input xx, the responsibility hi(x)h_i(x) of component gig_i is:

    hi(x)=P(xi)j=1NP(xj),where P(xi)=12πσx,i2exp((xμx,i)22σx,i2)h_i(x) = \frac{P(x \mid i)}{\sum_{j=1}^N P(x \mid j)}, \quad \text{where } P(x \mid i) = \frac{1}{\sqrt{2\pi \sigma_{x,i}^2}} \exp\left( -\frac{(x - \mu_{x,i})^2}{2\sigma_{x,i}^2} \right)

    For each component gig_i, the conditional output expectation y^i(x)\hat{y}_i(x) and conditional variance σy^,i2(x)\sigma_{\hat{y},i}^2(x) are:

    y^i(x)=μy,i+σxy,iσx,i2(xμx,i),σy^,i2(x)=σyx,i2ni(1+(xμx,i)2σx,i2)\hat{y}_i(x) = \mu_{y,i} + \frac{\sigma_{xy,i}}{\sigma_{x,i}^2}(x - \mu_{x,i}), \quad \sigma_{\hat{y},i}^2(x) = \frac{\sigma_{y \mid x,i}^2}{n_i} \left( 1 + \frac{(x - \mu_{x,i})^2}{\sigma_{x,i}^2} \right)

    where σyx,i2=σy,i2σxy,i2σx,i2\sigma_{y \mid x,i}^2 = \sigma_{y,i}^2 - \frac{\sigma_{xy,i}^2}{\sigma_{x,i}^2} is the conditional variance of yy given xx, and ni=j=1mP(xj,yji)k=1NP(xj,yjk)n_i = \sum_{j=1}^m \frac{P(x_j, y_j \mid i)}{\sum_{k=1}^N P(x_j, y_j \mid k)} represents the training data support for Gaussian gig_i.

    Assuming independence among the y^i(x)\hat{y}_i(x), the combined mixture output prediction and overall estimated model variance are:

    y^(x)=i=1Nhi(x)y^i(x),σy^2(x)=i=1Nhi(x)2σyx,i2ni(1+(xμx,i)2σx,i2)\hat{y}(x) = \sum_{i=1}^N h_i(x) \hat{y}_i(x), \quad \sigma_{\hat{y}}^2(x) = \sum_{i=1}^N \frac{h_i(x)^2 \sigma_{y \mid x,i}^2}{n_i} \left( 1 + \frac{(x - \mu_{x,i})^2}{\sigma_{x,i}^2} \right)

  3. Knowl 3 — Closed-Form Expected Variance Updates for Gaussian Mixture Active Learning

    theoretical result

    For a Mixture of Gaussians model, the estimated conditional distribution of an unobserved query label y~\tilde{y} given query input x~\tilde{x} is P(y~x~)=i=1Nh~iN(y^i(x~),σyx,i2(x~))P(\tilde{y} \mid \tilde{x}) = \sum_{i=1}^N \tilde{h}_i \mathcal{N}(\hat{y}_i(\tilde{x}), \sigma_{y \mid x,i}^2(\tilde{x})), where h~i=hi(x~)\tilde{h}_i = h_i(\tilde{x}). The expected new model variance at reference point xx resulting from querying candidate x~\tilde{x} can be computed exactly in closed form as:

    σ~y^2(x)=i=1Nhi(x)2σ~yx,i2ni+h~i(1+(xμx,i)2σx,i2)\langle \tilde{\sigma}_{\hat{y}}^2(x) \rangle = \sum_{i=1}^N \frac{h_i(x)^2 \langle \tilde{\sigma}_{y \mid x,i}^2 \rangle}{n_i + \tilde{h}_i} \left( 1 + \frac{(x - \mu_{x,i})^2}{\sigma_{x,i}^2} \right)

    where the expected updated component parameters are:

    σ~y,i2=niσy,i2ni+h~i+nih~i(σyx,i2(x~)+(y^i(x~)μy,i)2)(ni+h~i)2\langle \tilde{\sigma}_{y,i}^2 \rangle = \frac{n_i \sigma_{y,i}^2}{n_i + \tilde{h}_i} + \frac{n_i \tilde{h}_i \left( \sigma_{y \mid x,i}^2(\tilde{x}) + (\hat{y}_i(\tilde{x}) - \mu_{y,i})^2 \right)}{(n_i + \tilde{h}_i)^2}

    σ~xy,i=niσxy,ini+h~i+nih~i(x~μx,i)(y^i(x~)μy,i)(ni+h~i)2\langle \tilde{\sigma}_{xy,i} \rangle = \frac{n_i \sigma_{xy,i}}{n_i + \tilde{h}_i} + \frac{n_i \tilde{h}_i (\tilde{x} - \mu_{x,i})(\hat{y}_i(\tilde{x}) - \mu_{y,i})}{(n_i + \tilde{h}_i)^2}

    σ~xy,i2=σ~xy,i2+ni2h~i2σyx,i2(x~)(x~μx,i)2(ni+h~i)4\langle \tilde{\sigma}_{xy,i}^2 \rangle = \langle \tilde{\sigma}_{xy,i} \rangle^2 + \frac{n_i^2 \tilde{h}_i^2 \sigma_{y \mid x,i}^2(\tilde{x}) (\tilde{x} - \mu_{x,i})^2}{(n_i + \tilde{h}_i)^4}

    σ~yx,i2=σ~y,i2σ~xy,i2σx,i2\langle \tilde{\sigma}_{y \mid x,i}^2 \rangle = \langle \tilde{\sigma}_{y,i}^2 \rangle - \frac{\langle \tilde{\sigma}_{xy,i}^2 \rangle}{\sigma_{x,i}^2}

    When μx,i\mu_{x,i} and σx,i2\sigma_{x,i}^2 are also estimated from data, their updated expected values μ~x,i=niμx,i+h~ix~ni+h~i\tilde{\mu}_{x,i} = \frac{n_i \mu_{x,i} + \tilde{h}_i \tilde{x}}{n_i + \tilde{h}_i} and σ~x,i2=niσx,i2ni+h~i+nih~i(x~μx,i)2(ni+h~i)2\tilde{\sigma}_{x,i}^2 = \frac{n_i \sigma_{x,i}^2}{n_i + \tilde{h}_i} + \frac{n_i \tilde{h}_i (\tilde{x} - \mu_{x,i})^2}{(n_i + \tilde{h}_i)^2} substitute into the variance equations.

  4. Knowl 4 — Input Distribution Correction for Gaussian Mixture Active Learning

    model/method

    Because active data selection generates a training input distribution P(x~)P(\tilde{x}) that departs from the true input distribution P(x)P(x), estimating parameters directly from the active training data produces the conditioned distribution P(x~,yi)P(\tilde{x}, y \mid i) rather than P(x,yi)P(x, y \mid i). To correct for this sampling bias, the joint density estimate for Gaussian component ii is weighted by the ratio of the marginal input densities:

    P(x,yi)=P(x~,yi)P(xi)P(x~i)P(x, y \mid i) = P(\tilde{x}, y \mid i) \frac{P(x \mid i)}{P(\tilde{x} \mid i)}

    where P(x~i)P(\tilde{x} \mid i) is computed using the mean and variance of component ii on the training data, and P(xi)P(x \mid i) is computed using the mean and variance of component ii evaluated on an unlabelled reference dataset sampled from the known marginal input distribution P(x)P(x).

  5. Knowl 5 — Prediction and Output Variance Formulation for Locally Weighted Regression

    model/method

    In locally weighted regression (LOESS), predictions around a point xx are obtained by fitting a weighted linear regression over training samples (xi,yi)i=1m(x_i, y_i)_{i=1}^m using kernel weights hi(x)=exp(k(xxi)2)h_i(x) = \exp(-k(x - x_i)^2), where kk is a smoothing parameter. Setting total weight n=ihi(x)n = \sum_i h_i(x), the kernel-weighted means and covariances are:

    μx=ihixin,μy=ihiyin\mu_x = \frac{\sum_i h_i x_i}{n}, \quad \mu_y = \frac{\sum_i h_i y_i}{n}

    σx2=ihi(xiμx)2n,σy2=ihi(yiμy)2n,σxy=ihi(xiμx)(yiμy)n\sigma_x^2 = \frac{\sum_i h_i (x_i - \mu_x)^2}{n}, \quad \sigma_y^2 = \frac{\sum_i h_i (y_i - \mu_y)^2}{n}, \quad \sigma_{xy} = \frac{\sum_i h_i (x_i - \mu_x)(y_i - \mu_y)}{n}

    σyx2=σy2σxy2σx2\sigma_{y \mid x}^2 = \sigma_y^2 - \frac{\sigma_{xy}^2}{\sigma_x^2}

    The model prediction y^(x)\hat{y}(x) and estimated prediction variance σy^2(x)\sigma_{\hat{y}}^2(x) are given in closed form by:

    y^(x)=μy+σxyσx2(xμx)\hat{y}(x) = \mu_y + \frac{\sigma_{xy}}{\sigma_x^2}(x - \mu_x)

    σy^2(x)=σyx2n2(ihi2+(xμx)2σx2ihi2(xiμx)2σx2)\sigma_{\hat{y}}^2(x) = \frac{\sigma_{y \mid x}^2}{n^2} \left( \sum_i h_i^2 + \frac{(x - \mu_x)^2}{\sigma_x^2} \sum_i h_i^2 \frac{(x_i - \mu_x)^2}{\sigma_x^2} \right)

  6. Knowl 6 — Expected Variance Updates and Fast Moment Caching in LOESS Active Learning

    theoretical result

    For a LOESS model with kernel weight h~=h(x~x)\tilde{h} = h(\tilde{x} - x) assigned to a proposed candidate query x~\tilde{x}, the expected new output variance σ~y^2(x)\langle \tilde{\sigma}_{\hat{y}}^2(x) \rangle at reference point xx is:

    σ~y^2(x)=σ~yx2(n+h~)2[ihi2+h~2+(xμ~x)2σ~x2(ihi2(xiμ~x)2σ~x2+h~2(x~μ~x)2σ~x2)]\langle \tilde{\sigma}_{\hat{y}}^2(x) \rangle = \frac{\langle \tilde{\sigma}_{y \mid x}^2 \rangle}{(n + \tilde{h})^2} \left[ \sum_i h_i^2 + \tilde{h}^2 + \frac{(x - \tilde{\mu}_x)^2}{\tilde{\sigma}_x^2} \left( \sum_i h_i^2 \frac{(x_i - \tilde{\mu}_x)^2}{\tilde{\sigma}_x^2} + \tilde{h}^2 \frac{(\tilde{x} - \tilde{\mu}_x)^2}{\tilde{\sigma}_x^2} \right) \right]

    where updated parameters and expectations are:

    μ~x=nμx+h~x~n+h~,σ~x2=nσx2n+h~+nh~(x~μx)2(n+h~)2\tilde{\mu}_x = \frac{n \mu_x + \tilde{h}\tilde{x}}{n + \tilde{h}}, \quad \tilde{\sigma}_x^2 = \frac{n \sigma_x^2}{n + \tilde{h}} + \frac{n \tilde{h}(\tilde{x} - \mu_x)^2}{(n + \tilde{h})^2}

    σ~y2=nσy2n+h~+nh~(σyx~2+(y^(x~)μy)2)(n+h~)2\langle \tilde{\sigma}_y^2 \rangle = \frac{n \sigma_y^2}{n + \tilde{h}} + \frac{n \tilde{h} \left( \sigma_{y \mid \tilde{x}}^2 + (\hat{y}(\tilde{x}) - \mu_y)^2 \right)}{(n + \tilde{h})^2}

    σ~xy=nσxyn+h~+nh~(x~μx)(y^(x~)μy)(n+h~)2\langle \tilde{\sigma}_{xy} \rangle = \frac{n \sigma_{xy}}{n + \tilde{h}} + \frac{n \tilde{h}(\tilde{x} - \mu_x)(\hat{y}(\tilde{x}) - \mu_y)}{(n + \tilde{h})^2}

    σ~xy2=σ~xy2+n2h~2σyx~2(x~μx)2(n+h~)4,σ~yx2=σ~y2σ~xy2σ~x2\langle \tilde{\sigma}_{xy}^2 \rangle = \langle \tilde{\sigma}_{xy} \rangle^2 + \frac{n^2 \tilde{h}^2 \sigma_{y \mid \tilde{x}}^2 (\tilde{x} - \mu_x)^2}{(n + \tilde{h})^4}, \quad \langle \tilde{\sigma}_{y \mid x}^2 \rangle = \langle \tilde{\sigma}_y^2 \rangle - \frac{\langle \tilde{\sigma}_{xy}^2 \rangle}{\tilde{\sigma}_x^2}

    To avoid recomputing the sum ihi2(xiμ~x)2\sum_i h_i^2 (x_i - \tilde{\mu}_x)^2 in O(m)O(m) time for each candidate, the term is expanded as ihi2xi2+μ~x2ihi22μ~xihi2xi\sum_i h_i^2 x_i^2 + \tilde{\mu}_x^2 \sum_i h_i^2 - 2\tilde{\mu}_x \sum_i h_i^2 x_i, allowing evaluation in O(1)O(1) time by caching ihi2xi2\sum_i h_i^2 x_i^2, ihi2xi\sum_i h_i^2 x_i, and ihi2\sum_i h_i^2.

  7. Knowl 7 — Variance-Minimizing Kernel Smoothing Parameter Selection in LOESS

    model/method

    In locally weighted regression with kernel hi(x)=exp(k(xxi)2)h_i(x) = \exp(-k(x - x_i)^2), the smoothing parameter kk controls estimator locality. As kk decreases, the regression incorporates more global data, increasing total weight nn (which reduces variance σy^2\sigma_{\hat{y}}^2) but increasing the local conditional variance σyx2\sigma_{y \mid x}^2 due to nonlinear deviations (which increases variance σy^2\sigma_{\hat{y}}^2).

    The variance-minimizing selection criterion chooses kk to directly minimize estimated output variance σy^2\sigma_{\hat{y}}^2 over a set of reference points drawn from the input distribution P(x)P(x). This balances effective support against local bias without requiring assumptions about noise levels or cross-validation on an unrepresentative active training set distribution.

  8. Knowl 8 — Variance-Minimizing Active Query Selection Algorithm

    algorithm
    Input: Input distribution P(x)P(x), initial dataset D0\mathcal{D}_0, reference sample size R=64R = 64, candidate sample size C=64C = 64, iterations TT.
    Output: Augmented dataset DT\mathcal{D}_T and trained statistical model.
    Initialize DD0\mathcal{D} \leftarrow \mathcal{D}_0
    Fit model (Mixture of Gaussians via EM or LOESS via local weighted sums) on D\mathcal{D}
    for t=1t = 1 to TT do
        Sample RR reference points {xr}r=1R\{x_r\}_{r=1}^R from P(x)P(x)
        Sample CC candidate query points {x~c}c=1C\{\tilde{x}_c\}_{c=1}^C uniformly from input domain
        for each candidate x~c\tilde{x}_c do
            V(x~c)1Rr=1Rσ~y^2(xr)V(\tilde{x}_c) \leftarrow \frac{1}{R} \sum_{r=1}^R \langle \tilde{\sigma}_{\hat{y}}^2(x_r) \rangle
        end for
        Select optimal query x~argminx~cV(x~c)\tilde{x}^* \leftarrow \arg\min_{\tilde{x}_c} V(\tilde{x}_c)
        Query oracle to observe output y~\tilde{y}^* at x~\tilde{x}^*
        Update dataset DD{(x~,y~)}\mathcal{D} \leftarrow \mathcal{D} \cup \{(\tilde{x}^*, \tilde{y}^*)\}
        Retrain or update model parameters on D\mathcal{D}
    end for
    return D\mathcal{D} and trained model

    The algorithm iteratively draws an independent reference set to represent P(x)P(x), scores candidate queries by the Monte Carlo average of the closed-form expected variance σ~y^2\langle \tilde{\sigma}_{\hat{y}}^2 \rangle, selects the variance-minimizing point, and updates the model.

  9. Knowl 9 — Empirical Generalization on Robot Arm Kinematics Benchmark

    empirical result

    On the 2-degree-of-freedom robot arm kinematics domain (Arm2D) where inputs are joint angles (θ1,θ2)(\theta_1, \theta_2), outputs are tip coordinates (X1,X2)(X_1, X_2), and 1%1\% additive Gaussian noise is added to the inputs (inducing non-Gaussian output error):

    • For a Mixture of 60 Gaussians (trained with 20 EM iterations per step), the variance-minimizing active learning criterion produces a mean squared error (MSE) on independent test points that is consistently 1/31/3 of the MSE achieved by random data selection across training set sizes up to 500 points.
    • For LOESS regression with Gaussian kernels, both estimated output variance and MSE under variance-minimizing query selection are significantly lower than under random sampling.
    • LOESS regression significantly outperforms both the Mixture of Gaussians and feedforward neural networks in generalization accuracy and data efficiency on the Arm2D task.
  10. Knowl 10 — Computational Time Complexity of Statistical Active Learning

    data/table
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    Computation times measured on a Sun Sparc 10 workstation as a function of training set size mm (Mixture of Gaussians used 60 components trained for 20 iterations; reference times are per reference point, candidate times are per candidate point per reference point).

    For the Mixture of Gaussians, training time scales linearly with mm, but candidate evaluation per reference point is constant (1300μs1300\,\mu\text{s}) regardless of training set size. For LOESS, there is no explicit training phase; candidate evaluation scales with training size as 58+0.16mμs58 + 0.16m\,\mu\text{s} per candidate per reference point. For a setup with 100 training points, 64 reference points, and 64 candidate points, LOESS selects an optimal query in approximately 0.3 seconds.

Coverage note — The paper's background review of Optimal Experiment Design applied to feedforward neural networks (Fedorov 1972; MacKay 1992; Cohn 1994) was omitted from the main knowls because it represents existing literature rather than this paper's new contributions.

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Citation

MLA
Cohn, D. A., et al. “Active Learning with Statistical Models”. Journal of Artificial Intelligence Research, vol. 4, 1996, pp. 129–45, https://doi.org/10.1613/jair.295.
APA
Cohn, D. A., Ghahramani, Z., & Jordan, M. I. (1996). Active Learning with Statistical Models. Journal of Artificial Intelligence Research, 4, 129–145. https://doi.org/10.1613/jair.295
Chicago
Cohn, D. A., Z. Ghahramani, and M. I. Jordan. 1996. “Active Learning with Statistical Models”. Journal of Artificial Intelligence Research 4: 129–45. https://doi.org/10.1613/jair.295.
Harvard
Cohn, D.A., Ghahramani, Z. and Jordan, M.I. (1996) “Active Learning with Statistical Models”, Journal of Artificial Intelligence Research, 4, pp. 129–145. Available at: https://doi.org/10.1613/jair.295.
Vancouver
1. Cohn DA, Ghahramani Z, Jordan MI (1996) Active Learning with Statistical Models. Journal of Artificial Intelligence Research 4:129–145

BibTeX

@article{Cohn_1996, title={Active Learning with Statistical Models}, volume={4}, ISSN={1076-9757}, url={http://dx.doi.org/10.1613/jair.295}, DOI={10.1613/jair.295}, journal={Journal of Artificial Intelligence Research}, publisher={AI Access Foundation}, author={Cohn, D. A. and Ghahramani, Z. and Jordan, M. I.}, year={1996}, month=Mar, pages={129–145} }
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