{
    "original_study": {
        "claim": {
            "hypothesis": "Bilingual group membership will be positively associated with foreign language achievement when controlling for background variables.",
            "hypothesis_location": "the hypothesis is stated in the 1.4. Research questions section; it is also discussed in the abstract, introduction, section 1.2. Factors affecting language learning.",
            "statement": "Controlling for cognitive abilities, age, gender, socio-economic status, parental education, and indicators of cultural capital, the analysis revealed a general positive trend between bilingualism and English foreign language achievement (estimate = 2.68; p < .01).",
            "statement_location": "Table 3, Model B (Bilingual=1)",
            "study_type": "Observational" 
        },

        "data": { 
            "source": "the main source: Assessment of Reading and Mathematics Development Study (ELEMENT); for socioeconomic status data: International Socio-Economic Index.",
            "wave_or_subset": "the sixth grade elementary school cohort",
            "sample_size": "2835",
            "unit_of_analysis": "individual - German 6th graders nested in 134 elementary school classes",
            "access_details": "access details are not specified; no restrictions are mentioned, perhaps the datasets are open access.",
            "notes": "Data were collected from a sample of students from a major European city, with about 15% of students speaking a language other than German at home. The sample is representative of public elementary school students. English achievement was assessed with a Cloze test, scaled using one-parameter item response theory in ConQuest with weighted likelihood estimates (WLEs; mean = 100, SD = 20). General cognitive abilities were measured using a composite score from two subtests of the CFT4-12R (verbal and figural analogies). All analyses used five imputed datasets to replace missing values, based on a background model including individual-level factors (grades, self-concept, interest, motivation) and classroom-level factors (achievement, socio-economic status, percentage of students with immigration background). Results were combined using MPlus 5.21 with type = imputation."
        },

        "method": {
            "description": "The authors examined the effect of immigrant bilingualism on English as a foreign language achievement. They controlled for cognitive, demographic, and socio-cultural factors.",
            "steps": "1. Download the data and identify bilingual and monolingual groups based on language spoken at home. \n2. Exclude 111 students with no language information.\n3. Classify students into the monolingual group (n=1896) and the bilingual group (n=939).\n4. Assess English language achievement using a Cloze test, scaled with one-parameter item response theory in ConQuest using weighted likelihood estimates (WLEs; mean=100, SD=20).\n5. Measure general cognitive abilities (by the authors) using a composite score from two subtests of the CFT4-12R (verbal and figural analogies).\n6. Collect control variables from the dataset: age, gender, socio-economic status (ISEI data), parental education, and cultural capital. \n7. Handle missing data using multiple imputation.\n8. Run multiple linear regression in MPlus 5.21 with type = complex.",
            "models": "linear regression",
            "outcome_variable": "English achievement",
            "independent_variables": "bilingual group membership",
            "control_variables": "general cognitive abilities, gender, age, socio-economic status, parental education, and cultural capital",
            "tools_software": "For multiple regression: MPlus 5.21 taking into account the nested nature (students in classes) of the dataset (type = complex). For items scaling: ConQuest."
        },
        "results": {
            "summary": "After controlling for cognitive abilities, age, gender, socio-economic status, parental education, and indicators of cultural capital, bilingual students showed a general positive trend between bilingualism and English foreign language achievement (estimate = 2.68; p < .01).",
            "numerical_results": [ 
                {
                    "outcome_name": "English achievement",
                    "value": "2.68",
                    "unit": "points (raw Cloze test scores scaled to mean = 100, SD = 20)",
                    "effect_size": "not stated",
                    "confidence_interval": {
                        "lower": "not stated",
                        "upper": "not stated",
                        "level": "not stated"
                    },
                    "p_value": "< .01",
                    "statistical_significance": "true",
                    "direction": "positive"
                }
            ]
        },
       
        "metadata": {
            "original_paper_id": "http://dx.doi.org/10.1016/j.learninstruc.2014.12.001",
            "original_paper_title": "The effect of speaking a minority language at home on foreign language learning.",
            "original_paper_code": "not stated",
            "original_paper_data": "not stated"
        }
    }
}