急求3道英文数学题,急急急!谢谢达人QUESTION 1 IF A PROBABILITY DISTRIBUTION HAS A MEAN OF 7.4 AND A STANDARD DEVIATION OF 1.5, WHAT IS THE PROBABILITY THAT A RANDOM VARIABLE WILL HAVE A VALUE GREATER THAN 8 QUESTION 2 A TOTAL OF 36 STUDE

急求3道英文数学题,急急急!谢谢达人QUESTION 1 IF A PROBABILITY DISTRIBUTION HAS A MEAN OF 7.4 AND A STANDARD DEVIATION OF 1.5, WHAT IS THE PROBABILITY THAT A RANDOM VARIABLE WILL HAVE A VALUE GREATER THAN 8 QUESTION 2 A TOTAL OF 36 STUDE
急求3道英文数学题,急急急!谢谢达人
QUESTION 1
IF A PROBABILITY DISTRIBUTION HAS A MEAN OF 7.4 AND A STANDARD DEVIATION OF 1.5, WHAT IS THE PROBABILITY THAT A RANDOM VARIABLE WILL HAVE A VALUE GREATER THAN 8
QUESTION 2
A TOTAL OF 36 STUDENTS SUBMITTED AN ASSIGNMENT WORTH A TOTAL 100 MARKS. AFTER MARKING THE ASSIGNMENTS,IT WAS FOUND THAT THE ASSIGNMENT MARK MEAN FOR THE CLASS WAS 68.IF 27 STUDENTS PASSED(MARK OF 50 OR GREATER),WHAT IS THE STANDARD DEVIATION OF THE ASSIGNMENT MARKS?
QUESTION 3
FUTHER TO QUESTION 2, APPROXIMATELY HOW MANY STUDENTS WOULD YOU EXPECT TO HAVE ACHIEVED 40% OR GREATER ON THE ASSIGNMENT, BUT STILL FAILED?

急求3道英文数学题,急急急!谢谢达人QUESTION 1 IF A PROBABILITY DISTRIBUTION HAS A MEAN OF 7.4 AND A STANDARD DEVIATION OF 1.5, WHAT IS THE PROBABILITY THAT A RANDOM VARIABLE WILL HAVE A VALUE GREATER THAN 8 QUESTION 2 A TOTAL OF 36 STUDE
呃,其实我觉得你把这些题目好歹翻译出来吧再给人解答么...今晚闲的慌就给你翻一下吧...但是解题是指望不了我的,俺一个文科生,没学过概率.
另外,我同学说看这本书《概率论与数理统计》,用里面的公式很快能解完.
实在不行你拿上中文翻译问个理科学生,应该能很快解决的.加油吧～
1.如果概率分布中,一个平均值为7.4且一个标准偏差为1.5,那么随机变量值大于8的概率为多少? （翻译成“一个”是因为我不知道概率分布有几个平均值和标准偏差,如果只有一个那么这道题这样翻译：如果在概率分布中平均值为7.4且标准偏差为1.5,那么随机变量值大于8的概率为多少）
2.总共有36个学生做同一份作业,总分为100分.在判分后,发现全班的平均分为68.如果27个学生及格了（50分以上）,那么这份作业成绩的标准偏差为多少?
3.根据问题2,大约有多少学生你认为他们及格的期望值达到40％或更高,但实际上他们仍未及格?
翻译烂的话,不要bs俺,毕竟米学过高数,好多专业名词都不会翻...ORZ

用SPSS来做吧~我删了。

可以用规范书写吗，看起来好累耶！

Q1
sorry I'm not sure~~~
Q2
MARKS-----#OF STUDENT(FREQUENCY)-----X ------------FX^2
0-49--------9------------------(0+49.5)/2------9*((0+49.5)/2)^2
50-100-----27--------------...

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Q1
sorry I'm not sure~~~
Q2
MARKS-----#OF STUDENT(FREQUENCY)-----X ------------FX^2
0-49--------9------------------(0+49.5)/2------9*((0+49.5)/2)^2
50-100-----27------------------(49.5+100)/2 ----27*((49.5+100)/2)^2
total------36---------------------------------calculate it youself
than standard deviation=√((∑(fx^2)/∑f)-68^2)=calculate it youself
Q3
to solve this questions,the histogram should be used.
marks----#OF STUDENT-------width----------freq.den
0-49-------9----------49.5-0=49.5---------9/49.5=
50-100-----27-------100-49.5=50.5---------27/50.5=
note:the questions say 40≤x＜50
so the actual means is 39.5-50.5
frequency=(50.5-39.5)*(9/49.5)=......

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