设相互独立的随机变量序列<img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/4957bb46876c4ed4b78b98e36aa0ed0c.png?x-oss-process=image/sharpen,200"/>有相同的概率分布，且<img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/fc11fddc10c64d5c862139f70e1f0401.png?x-oss-process=image/sharpen,200"/>，<img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/1f18e3f5a9c746eba50673ca317d3d87.png?x-oss-process=image/sharpen,200"/>，<img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/d8f5537beb2346d295f3ef39ee72470a.png?x-oss-process=image/sharpen,200"/>，<img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/ae8554ddbcff4116919ac2fb7b384676.png?x-oss-process=image/sharpen,200"/>，记<img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/203045d069ce4002839dfb4887666cc0.png?x-oss-process=image/sharpen,200"/>，<img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/f11824e142134c05b6f8115108755f8c.png?x-oss-process=image/sharpen,200"/>为标准正态的分布函数，则<img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/c54d1973a7a0498e81eba43b6cea378c.png?x-oss-process=image/sharpen,200"/>等于（）