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Category: Probability and Statistics

Let-c-be-a-constant-Using-Var-X-E-X-E-X-2-show-that-a-Var-c-X-c-2-Var-X-b-Var-c-X-Var-X-

Question Number 6605 by WAI LIN last updated on 05/Jul/16 $${Let}\:{c}\:{be}\:{a}\:{constant}.\:{Using}\:{Var}\left({X}\right)\:=\:{E}\:\left[\left({X}−\:{E}\:\left[{X}\right]\right)^{\mathrm{2}} \right],\:{show}\:{that} \\ $$$$\left({a}\right)\:{Var}\left({c}\:{X}\right)\:=\:{c}^{\mathrm{2}} \:{Var}\left({X}\right); \\ $$$$\left({b}\right)\:{Var}\:\left(\:{c}+{X}\right)\:=\:{Var}\left({X}\right). \\ $$ Commented by prakash jain last updated…

If-the-density-function-of-X-equals-f-x-c-e-2x-0-lt-x-lt-0-x-lt-0-find-c-What-is-P-X-gt-2-

Question Number 6604 by WAI LIN last updated on 05/Jul/16 $${If}\:{the}\:{density}\:{function}\:{of}\:{X}\:{equals} \\ $$$${f}\left({x}\right)\:=\:\begin{cases}{{c}\:{e}^{−\mathrm{2}{x}} \:,\:\mathrm{0}<{x}<\infty}\\{\mathrm{0}\:,\:\:\:\:\:\:\:\:\:\:{x}<\mathrm{0}}\end{cases} \\ $$$${find}\:{c}.\:{What}\:{is}\:{P}\left\{{X}>\mathrm{2}\right\}? \\ $$ Commented by prakash jain last updated on…

A-party-of-7-members-is-to-be-chosen-from-a-group-of-6-ladies-and-5-gents-In-how-many-ways-can-the-party-be-formed-if-it-is-to-contain-i-exactly-4-ladies-i-at-least-4-ladies-i-at

Question Number 6098 by Rasheed Soomro last updated on 13/Jun/16 $$\mathrm{A}\:\mathrm{party}\:\mathrm{of}\:\:\mathrm{7}\:\:\:\mathrm{members}\:\mathrm{is}\:\mathrm{to}\:\mathrm{be}\:\mathrm{chosen} \\ $$$$\mathrm{from}\:\mathrm{a}\:\mathrm{group}\:\mathrm{of}\:\:\mathrm{6}\:\:\mathrm{ladies}\:\mathrm{and}\:\:\mathrm{5}\:\:\mathrm{gents}. \\ $$$$\mathrm{In}\:\mathrm{how}\:\mathrm{many}\:\mathrm{ways}\:\mathrm{can}\:\mathrm{the}\:\mathrm{party}\:\mathrm{be} \\ $$$$\mathrm{formed}\:\mathrm{if}\:\mathrm{it}\:\mathrm{is}\:\mathrm{to}\:\mathrm{contain} \\ $$$$\left(\mathrm{i}\right)\:\:\:\mathrm{exactly}\:\mathrm{4}\:\:\mathrm{ladies} \\ $$$$\left(\mathrm{i}\right)\:\:\:\mathrm{at}\:\mathrm{least}\:\mathrm{4}\:\:\mathrm{ladies} \\ $$$$\left(\mathrm{i}\right)\:\:\:\mathrm{at}\:\mathrm{most}\:\mathrm{4}\:\:\mathrm{ladies}\:? \\ $$…

If-four-people-all-said-HELLO-to-each-other-once-how-many-times-would-the-word-HELLO-be-spoken-

Question Number 5897 by sanusihammed last updated on 04/Jun/16 $${If}\:{four}\:{people}\:{all}\:{said}\:\:{HELLO}\:{to}\:{each}\:{other}\:{once}.\:{how}\:{many}\: \\ $$$${times}\:{would}\:{the}\:{word}\:\:{HELLO}\:\:{be}\:{spoken}\:? \\ $$ Answered by FilupSmith last updated on 04/Jun/16 $${person}\:\mathrm{1}\:{talks}\:{to}\:\mathrm{3}\:{people} \\ $$$${person}\:\mathrm{2}\:{talks}\:{to}\:\mathrm{2}\:{people} \\…