Fatal error: Uncaught Error: Call to a member function fetch_array() on boolean in /www/wwwroot/www.shzkw.org/phpcms/libs/classes/db_mysqli.class.php:153
Stack trace:
#0 /www/wwwroot/www.shzkw.org/phpcms/model/get_model.class.php(30): db_mysqli->fetch_next()
#1 /www/wwwroot/www.shzkw.org/caches/caches_template/default/content/yzb_exam_detail.php(153): get_model->fetch_next()
#2 /www/wwwroot/www.shzkw.org/phpcms/modules/yzb/exam.php(291): include('/www/wwwroot/ww...')
#3 /www/wwwroot/www.shzkw.org/phpcms/libs/classes/application.class.php(31): exam->detail()
#4 /www/wwwroot/www.shzkw.org/phpcms/libs/classes/application.class.php(19): application->init()
#5 /www/wwwroot/www.shzkw.org/phpcms/base.php(134): application->__construct()
#6 /www/wwwroot/www.shzkw.org/phpcms/base.php(85): pc_base::_load_class('application', 'libs/classes', 1)
#7 /www/wwwroot/www.shzkw.org/phpcms/base.php(76): pc_base::load_sys_class('application')
#8 /www/wwwroot/www.shzkw.org/index.php(15): pc_base::creat_app()
#9 {main}
thrown in /www/wwwroot/www.shzkw.org/phpcms/libs/classes/db_mysqli.class.php on line 153
一R控制图控制某种零件的加工外径。现从生产过程中每次抽样6件,共抽取25次。已测算出样本平均值总和习
=550mm,样本极差总和
=130nm.试计算
―R控制图的中心线和上下控制界值。
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