作业帮概率统计 外交考试 .上课时没听,英语也看不懂.先给英文题目,求大神给详细中文解释.
来源：学生作业帮 编辑：作业帮 分类：英语作业 时间：2024/05/21 07:50:49
A simple financial model is proposed to describe changes in two stock prices from time t to time t+1.At time t,the price of one share in the first stock is 180p,and the price of one share in the second stock is 230p. Let X be the price (in pence) of one share in the first stock at time t+1, and Y be the price (in pence) of one share in the second stock at time t+1.The joint probability mass function of X and Y is tatulated below.
(i) Write out, in a suitable table, the marginal probability mass function of Y. (这一问我已经知道答案是什么了,但是不理解什么是 marginal probability mass function,求简显易懂的中文详解,不要百度翻译!）
(ii)Find the variance of Y. State the unit of measurement of the variance.(这一问不懂最后一句话是什么意思,答案给的就一句话：unit of measurement is pence squared)
(iii)If it is known that the first stock has increased in price, what is the probability that the second stock has also increased in price?(完全不懂,题目也看不太懂）
(iv)Without doing any further calculation, are X and Y independent? Briefly justify your answer.
(v) By inspecting the joint probability mass function, but without doing any calculations, state whether the covariance between X and Y will be positive or negative, briefly explaining your answer.
跪求大神帮忙!考试在即,不得不抓紧啊!谢谢了
II) 方差的单位
III) 如果第一支股票上涨,同时第二支股票也上张的概率 =0.07
IV) 不独立, 因为P(X,Y)≠P(X)P(Y)
V) 正值,因为X上涨的概率比下降大,Y上涨下降的概率相同,没有出现反趋势