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How Efficacy Studies Can Help Decision-makers Decide if a Product is Likely to Work in Their Schools

We and our colleagues have been working on translating the results of rigorous studies of the impact of educational products, programs, and policies for people in school districts who are making the decisions whether to purchase or even just try out—pilot—the product. We are influenced by Stanford University Methodologist Lee Cronbach, especially his seminal book (1982) and article (1975) where he concludes “When we give proper weight to local conditions, any generalization is a working hypothesis, not a conclusion…positive results obtained with a new procedure for early education in one community warrant another community trying it. But instead of trusting that those results generalize, the next community needs its own local evaluation” (p. 125). In other words, we consider even the best designed experiment to be like a case study, as much about the local and moderating role of context, as about the treatment when interpreting the causal effect of the program.

Following the focus on context, we can consider characteristics of the people and of the institution where the experiment was conducted to be co-causes of the result that deserve full attention—even though, technically, only the treatment, which was randomly assigned was controlled. Here we argue that any generalization from a rigorous study, where the question is whether the product is likely to be worth trying in a new district, must consider the full context of the study.

Technically, in the language of evaluation research, these differences in who or where the product or “treatment” works are called “interaction effects” between the treatment and the characteristic of interest (e.g., subgroups of students by demographic category or achievement level, teachers with different skills, or bandwidth available in the building). The characteristic of interest can be called a “moderator”, since it changes, or moderates, the impact of the treatment. An interaction reveals if there is differential impact and whether a group with a particular characteristic is advantaged, disadvantaged, or unaffected by the product.

The rules set out by The Department of Education’s What Works Clearinghouse (WWC) focus on the validity of the experimental conclusion: Did the program work on average compared to a control group? Whether it works better for poor kids than for middle class kids, works better for uncertified teachers versus veteran teachers, increases or closes a gap between English learners and those who are proficient, are not part of the information provided in their reviews. But these differences are exactly what buyers need in order to understand whether the product is a good candidate for a population like theirs. If a program works substantially better for English proficient students than for English learners, and the purchasing school has largely the latter type of student, it is important that the school administrator know the context for the research and the result.

The accuracy of an experimental finding depends on it not being moderated by conditions. This is recognized with recent methods of generalization (Tipton, 2013) that essentially apply non-experimental adjustments to experimental results to make them more accurate and more relevant to specific local contexts.

Work by Jaciw (2016a, 2016b) takes this one step further.

First, he confirms the result that if the impact of the program is moderated, and if moderators are distributed differently between sites, then an experimental result from one site will yield a biased inference for another site. This would be the case, for example, if the impact of a program depends on individual socioeconomic status, and there is a difference between the study and inference sites in the proportion of individuals with low socioeconomic status. Conditions for this “external validity bias” are well understood, but the consequences are addressed much less often than the usual selection bias. Experiments can yield accurate results about the efficacy of a program for the sample studied, but that average may not apply either to a subgroup within the sample or to a population outside the study.

Second, he uses results from a multisite trial to show empirically that there is potential for significant bias when inferring experimental results from one subset of sites to other inference sites within the study; however, moderators can account for much of the variation in impact across sites. Average impact findings from experiments provide a summary of whether a program works, but leaves the consumer guessing about the boundary conditions for that effect—the limits beyond which the average effect ceases to apply. Cronbach was highly aware of this, titling a chapter in his 1982 book “The Limited Reach of Internal Validity”. Using terms like “unbiased” to describe impact findings from experiments is correct in a technical sense (i.e., the point estimate, on hypothetical repeated sampling, is centered on the true average effect for the sample studied), but it can impart an incorrect sense of the external validity of the result: that it applies beyond the instance of the study.

Implications of the work cited, are, first, that it is possible to unpack marginal impact estimates through subgroup and moderator analyses to arrive at more-accurate inferences for individuals. Second, that we should do so—why obscure differences by paying attention to only the grand mean impact estimate for the sample? And third, that we should be planful in deciding which subgroups to assess impacts for in the context of individual experiments.

Local decision-makers’ primary concern should be with whether a program will work with their specific population, and to ask for causal evidence that considers local conditions through the moderating role of student, teacher, and school attributes. Looking at finer differences in impact may elicit criticism that it introduces another type of uncertainty—specifically from random sampling error—which may be minimal with gross impacts and large samples, but influential when looking at differences in impact with more and smaller samples. This is a fair criticism, but differential effects may be less susceptible to random perturbations (low power) than assumed, especially if subgroups are identified at individual levels in the context of cluster randomized trials (e.g., individual student-level SES, as opposed to school average SES) (Bloom, 2005; Jaciw, Lin, & Ma, 2016).

References:
Bloom, H. S. (2005). Randomizing groups to evaluate place-based programs. In H. S. Bloom (Ed.), Learning more from social experiments. New York: Russell Sage Foundation.

Cronbach, L. J. (1975). Beyond the two disciplines of scientific psychology. American Psychologist, 116-127.

Cronbach, L. J. (1982). Designing evaluations of educational and social programs. San Francisco, CA: Jossey-Bass.

Jaciw, A. P. (2016). Applications of a within-study comparison approach for evaluating bias in generalized causal inferences from comparison group studies. Evaluation Review, (40)3, 241-276. Retrieved from http://erx.sagepub.com/content/40/3/241.abstract

Jaciw, A. P. (2016). Assessing the accuracy of generalized inferences from comparison group studies using a within-study comparison approach: The methodology. Evaluation Review, (40)3, 199-240. Retrieved from http://erx.sagepub.com/content/40/3/199.abstract

Jaciw, A., Lin, L., & Ma, B. (2016). An empirical study of design parameters for assessing differential impacts for students in group randomized trials. Evaluation Review. Retrieved from http://erx.sagepub.com/content/early/2016/10/14/0193841X16659600.abstract

Tipton, E. (2013). Improving generalizations from experiments using propensity score subclassification: Assumptions, properties, and contexts. Journal of Educational and Behavioral Statistics, 38, 239-266.

2018-01-16

The Value of Looking at Local Results

The report we released today has an interesting history that shows the value of looking beyond the initial results of an experiment. Later this week, we are presenting a paper at AERA entitled “In School Settings, Are All RCTs Exploratory?” The findings we report from our experiment with an iPad application were part of the inspiration for this. If Riverside Unified had not looked at its own data, we would not, in the normal course of data analysis, have broken the results out by individual districts, and our conclusion would have been that there was no discernible impact of the app. We can cite many other cases where looking at subgroups leads us to conclusions different from the conclusion based on the result averaged across the whole sample. Our report on AMSTI is another case we will cite in our AERA paper.

We agree with the Institute of Education Sciences (IES) in taking a disciplined approach in requiring that researchers “call their shots” by naming the small number of outcomes considered most important in any experiment. All other questions are fine to look at but fall into the category of exploratory work. What we want to guard against, however, is the implication that answers to primary questions, which often are concerned with average impacts for the study sample as a whole, must apply to various subgroups within the sample, and therefore can be broadly generalized by practitioners, developers, and policy makers.

If we find an average impact but in exploratory analysis discover plausible, policy-relevant, and statistically strong differential effects for subgroups, then some doubt about completeness may be cast on the value of the confirmatory finding. We may not be certain of a moderator effect—for example—but once it comes to light, the value of the average impact can also be considered incomplete or misleading for practical purposes. If it is necessary to conduct an additional experiment to verify a differential subgroup impact, the same experiment may verify that the average impact is not what practitioners, developers, and policy makers should be concerned with.

In our paper at AERA, we are proposing that any result from a school-based experiment should be treated as provisional by practitioners, developers, and policy makers. The results of RCTs can be very useful, but the challenges of generalizability of the results from even the most stringently designed experiment mean that the results should be considered the basis for a hypothesis that the intervention may work under similar conditions. For a developer considering how to improve an intervention, the specific conditions under which it appeared to work or not work is the critical information to have. For a school system decision maker, the most useful pieces of information are insight into subpopulations that appear to benefit and conditions that are favorable for implementation. For those concerned with educational policy, it is often the case that conditions and interventions change and develop more rapidly than research studies can be conducted. Using available evidence may mean digging through studies that have confirmatory results in contexts similar or different from their own and examining exploratory analyses that provide useful hints as to the most productive steps to take next. The practitioner in this case is in a similar position to the researcher considering the design of the next experiment. The practitioner also has to come to a hypothesis about how things work as the basis for action.

2012-04-01

Study of Alabama STEM Initiative Finds Positive Impacts

On February 21, 2012 the U.S. Department of Education released the final report of an experiment that Empirical Education has been working on for the last six years. The report, titled Evaluation of the Effectiveness of the Alabama Math, Science, and Technology Initiative (AMSTI) is now available on the Institute of Education Sciences website. The Alabama State Department of Education held a press conference to announce the findings, attended by Superintendent of Education Bice, staff of AMSTI, along with educators, students, and co-principal investigator of the study, Denis Newman, CEO of Empirical Education. The press release issued by the Alabama State Department of Education and a WebEx presentation provide more detail on the study’s findings.

AMSTI was developed by the state of Alabama and introduced in 2002 with the goal of improving mathematics and science achievement in the state’s K-12 schools. Empirical Education was primarily responsible for conducting the study—including the design, data collection, analysis, and reporting—under its subcontract with the Regional Education Lab, Southeast (the study was initiated through a research grant to Empirical). Researchers from Academy of Education Development, Abt Associates, and ANALYTICA made important contributions to design, analysis and data collection.

The findings show that after one year, students in the 41 AMSTI schools experienced an impact on mathematics achievement equivalent to 28 days of additional student progress over students receiving conventional mathematics instruction. The study found, after one year, no difference for science achievement. It also found that AMSTI had an impact on teachers’ active learning classroom practices in math and science that, according to the theory of action posited by AMSTI, should have an impact on achievement. Further exploratory analysis found effects for student achievement in both mathematics and science after two years. The study also explored reading achievement, where it found significant differences between the AMSTI and control groups after one year. Exploration of differential effect for student demographic categories found consistent results for gender, socio-economic status, and pretest achievement level for math and science. For reading, however, the breakdown by student ethnicity suggests a differential benefit.

Just about everybody at Empirical worked on this project at one point or another. Besides the three of us (Newman, Jaciw and Zacamy) who are listed among the authors, we want to acknowledge past and current employees whose efforts made the project possible: Jessica Cabalo, Ruthie Chang, Zach Chin, Huan Cung, Dan Ho, Akiko Lipton, Boya Ma, Robin Means, Gloria Miller, Bob Smith, Laurel Sterling, Qingfeng Zhao, Xiaohui Zheng, and Margit Zsolnay.

With solid cooperation of the state’s Department of Education and the AMSTI team, approximately 780 teachers and 30,000 upper-elementary and middle school students in 82 schools from five regions in Alabama participated in the study. The schools were randomized into one of two categories: 1) Those who received AMSTI starting the first year, or 2) Those who received “business as usual” the first year and began participation in AMSTI the second year. With only a one-year delay before the control group entered treatment, the two-year impact was estimated using statistical techniques developed by, and with the assistance of our colleagues at Abt Associates. Academy for Education Development assisted with data collection and analysis of training and program implementation.

Findings of the AMSTI study will also be presented at the Society for Research on Educational Effectiveness (SREE) Spring Conference taking place in Washington D.C. from March 8-10, 2012. Join Denis Newman, Andrew Jaciw, and Boya Ma on Friday March 9, 2012 from 3:00pm-4:30pm, when they will present findings of their study titled, “Locating Differential Effectiveness of a STEM Initiative through Exploration of Moderators.” A symposium on the study, including the major study collaborators, will be presented at the annual conference of the American Educational Research Association (AERA) on April 15, 2012 from 2:15pm-3:45pm at the Marriott Pinnacle ⁄ Pinnacle III in Vancouver, Canada. This session will be chaired by Ludy van Broekhuizen (director of REL-SE) and will include presentations by Steve Ricks (director of AMSTI); Jean Scott (SERVE Center at UNCG); Denis Newman, Andrew Jaciw, Boya Ma, and Jenna Zacamy (Empirical Education); Steve Bell (Abt Associates); and Laura Gould (formerly of AED). Sean Reardon (Stanford) will serve as the discussant. A synopsis of the study will also be included in the Common Guidelines for Education Research and Development.

2012-02-21

Exploration in the World of Experimental Evaluation

Our 300+ page report makes a good start. But IES, faced with limited time and resources to complete the many experiments being conducted within the Regional Education Lab system, put strict limits on the number of exploratory analyses researchers could conduct. We usually think of exploratory work as questions to follow up on puzzling or unanticipated results. However, in the case of the REL experiments, IES asked researchers to focus on a narrow set of “confirmatory” results and anything else was considered “exploratory,” even if the question was included in the original research design.

The strict IES criteria were based on the principle that when a researcher is using tests of statistical significance, the probability of erroneously concluding that there is an impact when there isn’t one increases with the frequency of the tests. In our evaluation of AMSTI, we limited ourselves to only four such “confirmatory” (i.e., not exploratory) tests of statistical significance. These were used to assess whether there was an effect on student outcomes for math problem-solving and for science, and the amount of time teachers spent on “active learning” practices in math and in science. (Technically, IES considered this two sets of two, since two were the primary student outcomes and two were the intermediate teacher outcomes.) The threshold for significance was made more stringent to keep the probability of falsely concluding that there was a difference for any of the outcomes at 5% (often expressed as p < .05).

While the logic for limiting the number of confirmatory outcomes is based on technical arguments about adjustments for multiple comparisons, the limit on the amount of exploratory work was based more on resource constraints. Researchers are notorious (and we don’t exempt ourselves) for finding more questions in any study than were originally asked. Curiosity-based exploration can indeed go on forever. In the case of our evaluation of AMSTI, however, there were a number of fundamental policy questions that were not answered either by the confirmatory or by the exploratory questions in our report. More research is needed.

Take the confirmatory finding that the program resulted in the equivalent of 28 days of additional math instruction (or technically an impact of 5% of a standard deviation). This is a testament to the hard work and ingenuity of the AMSTI team and the commitment of the school systems. From a state policy perspective, it gives a green light to continuing the initiative’s organic growth. But since all the schools in the experiment applied to join AMSTI, we don’t know what would happen if AMSTI were adopted as the state curriculum requiring schools with less interest to implement it. Our results do not generalize to that situation. Likewise, if another state with different levels of achievement or resources were to consider adopting it, we would say that our study gives good reason to try it but, to quote Lee Cronbach, a methodologist whose ideas increasingly resonate as we translate research into practice: “…positive results obtained with a new procedure for early education in one community warrant another community trying it. But instead of trusting that those results generalize, the next community needs its own local evaluation” (Cronbach, 1975, p. 125).

The explorations we conducted as part of the AMSTI evaluation did not take the usual form of deeper examinations of interesting or unexpected findings uncovered during the planned evaluation. All the reported explorations were questions posed in the original study plan. They were defined as exploratory either because they were considered of secondary interest, such as the outcome for reading, or because they were not a direct causal result of the randomization, such as the results for subgroups of students defined by different demographic categories. Nevertheless, exploration of such differences is important for understanding how and for whom AMSTI works. The overall effect, averaging across subgroups, may mask differences that are of critical importance for policy

Readers interested in the issue of subgroup differences can refer to Table 6.11. Once differences are found in groups defined in terms of individual student characteristics, our real exploration is just beginning. For example, can the difference be accounted for by other characteristics or combinations of characteristics? Is there something that differentiates the classes or schools that different students attend? Such questions begin to probe additional factors that can potentially be addressed in the program or its implementation. In any case, the report just released is not the “final report.” There is still a lot of work necessary to understand how any program of this sort can continue to be improved.

2012-02-14

New Reports Show Positive Results for Elementary Reading Program

Two studies of the Treasures reading program from McGraw-Hill are now posted on our reports page. Treasures is a basal reading program for students in grades K–6. Although the first study was a multi-site study while the second was conducted in the Osceola school district, both found positive impacts on reading achievement in grades 3–5.

The primary data for the first study were scores supplied with district permission by Northwest Evaluation Association from their MAP reading test. The study uses a quasi-experimental comparison group design based on 35 Treasures and 48 comparison schools primarily in the midwest. The study found that Treasures had a positive impact on overall elementary student reading scores, the strongest effect being observed for grade 5.

The second study’s data were provided by the Osceola school district and consist of demographic information, FCAT test scores, and information on student transfers during the year (between schools within the districts and from other districts). The dataset for this time series design covered five consecutive school years from 2005–06 to 2009–10, including two years prior to introduction of the intervention and three years after the introduction. The study included exploration of moderators that demonstrated a stronger positive effect for students with disabilities and English learners than the rest of the student population. We also found a stronger positive impact on girls than on boys.

Check back for results from follow-up studies, which are currently underway in other states and districts.

2011-09-21
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