标准分计算两种实现方式，计算公式见百度百科。
1 直接借助sql，写一个方法

 /**
 * 计算生成标准分
 * @return
 */
public int doGenerateStandScore() {
    StringBuilder sql = new StringBuilder();
    sql.append("    SELECT                                                                                   ");
    sql.append("        avg(er.total_score) avgScore,                                                        ");
    sql.append("        STD(er.total_score) standardDeviation,                                               ");
    sql.append("        39/((max(total_score) - avg(er.total_score))/STD(er.total_score)-                    ");
    sql.append("        (50 - avg(er.total_score))/STD(er.total_score)) coefficient,                         ");
    sql.append("        60 - (50 - avg(er.total_score))/STD(er.total_score)*39/((max(total_score) -          ");
    sql.append("        avg(er.total_score))/STD(er.total_score) -                                           ");
    sql.append("        (50 - avg(er.total_score))/STD(er.total_score)) referPoints                          ");
    sql.append("    FROM                                                                                     ");
    sql.append("        exam_reserve er                                                                      ");
    sql.append("    INNER JOIN exam_batch bat ON bat.id = er.fk_exam_batch_id                                ");
    sql.append("    INNER JOIN enum_const active ON active.id = bat.flag_active                              ");
    sql.append("    WHERE                                                                                    ");
    sql.append("        active. CODE = '1'                                                                   ");
    sql.append("    AND er.total_score IS NOT NULL                                                           ");
        // 平均分，方差，扩大系数，基准分
    Map<String, Object> resultMap =  myGeneralDao.getOneMapBySQL(sql.toString());
    if (MapUtils.isEmpty(resultMap)) {
        throw new ServiceException("没有需要合成标准分的数据");
    }
    BigDecimal avgScore = new BigDecimal(String.valueOf(resultMap.get("avgScore")));
    BigDecimal standardDeviation = new BigDecimal(String.valueOf(resultMap.get("standardDeviation")));
    BigDecimal coefficient = new BigDecimal(String.valueOf(resultMap.get("coefficient")));
    BigDecimal referPoints = new BigDecimal(String.valueOf(resultMap.get("referPoints")));
    sql.delete(0, sql.length());
    sql.append("    UPDATE exam_reserve er                                                     ");
    sql.append("    INNER JOIN exam_batch bat ON bat.id = er.fk_exam_batch_id                  ");
    sql.append("    INNER JOIN enum_const active ON active.id = bat.flag_active                ");
    sql.append("    SET er.standard_score = round((er.total_score - ?)/? * ? + ?)              ");
    sql.append("    WHERE                                                                      ");
    sql.append("        active. CODE = '1'                                                     ");
    sql.append("    AND er.total_score IS NOT NULL                                             ");
    return myGeneralDao.executeBySQL(sql.toString(), avgScore, standardDeviation, coefficient, referPoints);
}

2 java代码方式写工具方法。

package plugins;

import com.ss.excel.db.DB;

import java.math.BigDecimal;
import java.sql.SQLException;
import java.util.List;

/**
 * 计算标准分  （此处严格来讲应该将double改成BigDecimal类型）
 *
 * @author ss
 */
public class StandardScoreUtils {

    public static void main(String[] args) throws SQLException {
        List<Double> rawScores = DB.query(sql);// sql为查询的结果集
        double avgScore = calculateScoreMean(rawScores);
        System.out.println("平均分----" + avgScore);

        double standardDeviation = calculateSTD(rawScores, avgScore);
        System.out.println("标准差----" + standardDeviation);

        System.out.println("****************************************************************************");
        for (Double rawScore : rawScores) {
            double standardScore = calculateStandardScore(rawScore, standardDeviation, avgScore);
            double result = new BigDecimal(standardScore).setScale(2, BigDecimal.ROUND_HALF_UP).doubleValue();
            System.out.println("原始分：" + rawScore + "---- 标准分四舍五入：" + result + "----标准分：" + standardScore);
        }
    }

    /**
     * 计算平均分
     * @param rawScores
     * @return
     */
    public static double calculateScoreMean(List<Double> rawScores) {
        double scoreAll = 0.0;
        for (Double score : rawScores) {
            scoreAll += score;
        }
        return scoreAll/rawScores.size();
    }

    /**
     * 计算标准差
     * @param rawScores
     * @param avgScore
     * @return
     */
    public static double calculateSTD(List<Double> rawScores, double avgScore) {
        double allSquare = 0.0;
        for (Double rawScore : rawScores) {
            allSquare += (rawScore - avgScore) * (rawScore - avgScore);
        }
        return Math.sqrt(allSquare/rawScores.size());
    }

    /**
     * 计算标准分
     * @param score
     * @param standardDeviation
     * @param avgScore
     * @return
     */
    public static double calculateStandardScore(double score, double standardDeviation, double avgScore) {
        double standardScore = (score - avgScore)/standardDeviation;
        return standardScore;
    }

}