# probability QWatch

#1

The discrete random variable X is such that X ~ B(10, 0.34). Calculate

(i) P(X = 3),
(ii) P(X > 1),
(iii) P(4 ? X < 7),
(iv) E(X).

if you know, at least tell me what they mean by X ~ B(10, 0.34).
thanks
0
#2
its not probability, its binomial distribution! sorry.
0
7 years ago
#3
Binomial distribution: X~B(n,p)
n= number of trials
p= probability of success
0
7 years ago
#4
(Original post by bobthebuilder)

The discrete random variable X is such that X ~ B(10, 0.34). Calculate

(i) P(X = 3),
(ii) P(X > 1),
(iii) P(4 ? X < 7),
(iv) E(X).

if you know, at least tell me what they mean by X ~ B(10, 0.34).
thanks
(i) Use nCx p^x q^(n-x)
So, do 10C3 (0.34)^3 (0.66)^7

Is this for the S1 Paper?
0
7 years ago
#5
(Original post by HollieMcLean)
(i) Use nCx p^x q^(n-x)
So, do 10C3 (0.34)^3 (0.66)^7

Is this for the S1 Paper?
I believe this is S2 edexcel.

Here is how you solve each question:

i) see post No. 4. Its in your formulae book.

ii) p(x>1) = 1 - p(x<[or equal to]1) = 1 - (p(x=0) + p(x=1) - use the forumlae in post No.4 given to work out those two values of p(x=0) and p(x=1)

iii) p(4<x<7) = p(x<7) - p(x<4) [I think]

iv) E(X) = mean = np = 10 x 0.34

Strange because you cannot use tables, I think it would be easier to use it on part iii). But it goes up by 0.05 each time in binomial tables.
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#6
(Original post by mr tim)
I believe this is S2 edexcel.

Here is how you solve each question:

i) see post No. 4. Its in your formulae book.

ii) p(x>1) = 1 - p(x<[or equal to]1) = 1 - (p(x=0) + p(x=1) - use the forumlae in post No.4 given to work out those two values of p(x=0) and p(x=1)

iii) p(4<x<7) = p(x<7) - p(x<4) [I think]

iv) E(X) = mean = np = 10 x 0.34

Strange because you cannot use tables, I think it would be easier to use it on part iii). But it goes up by 0.05 each time in binomial tables.
thak you so much!! this really helped! thanks =)
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#7
(Original post by HollieMcLean)
(i) Use nCx p^x q^(n-x)
So, do 10C3 (0.34)^3 (0.66)^7

Is this for the S1 Paper?
thanks, yes it is S1!
0
7 years ago
#8
(Original post by bobthebuilder)
thanks, yes it is S1!
I thought it might be, I'm a 2nd year resitting the Stats module so if you need any more help just ask
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