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April 28, 2015

April 28, 2015

Posted by **Nora 57** on Saturday, June 1, 2013 at 4:48pm.

(a) Calculate the probability of x for: n = 1, x = 0, p = 0.15

P(x) = Changed: Your submitted answer was incorrect. 0.15 x 0 = 0 .

(b) Calculate the probability of x for: n = 3, x = 3, p = 0.15

P(x) = Incorrect: Your answer is incorrect. . 0.15 x 3 = 0.45

(c) Calculate the probability of x for: n = 5, x = 0, p = 0.8

P(x) = Correct: Your answer is correct. . 0.8 x 0 = 0

(d) Calculate the probability of x for: n = 1, x = 1, p = 0.4

P(x) = Correct: Your answer is correct. . 0.4 x 1 =0.40

(e) Calculate the probability of x for: n = 3, x = 1, p = 0.45

P(x) = Incorrect: Your answer is incorrect. . 0.45 x 1 =0.45

(f) Calculate the probability of x for: n = 6, x = 6, p = 0.25

P(x) = Incorrect: Your answer is incorrect. . 0.25 x 6 = 1.50

This is what I got when I redone them.

- math answer check -
**MathMate**, Saturday, June 1, 2013 at 10:43pmFor a binomial distribution, the outcomes are either 1 (success) or zero (failure).

The probability of success (outcome =1)of EACH step (out of n steps) is p and remains unchanged over the duration of the experiment.

The probability of failure (outcome =0) of EACH step (out of n steps) is q=1-p and remains unchanged over the duration of the experiment.

The probability of r successes in an n-step experiment is given by:

Bin(n,p,x)

=nCx p^x q^(n-x)

where nCx = n!/((n-x)!x!)

and x=number of successes

(a)

n=1, p=0.15, q=0.85

r=0 (0 success)

P(1,0,0.15)

=1C0 0.15^0 0.85^1

=1*1*0.85

=0.85

(b)

n=3, x=3, p=0.15

P(3,3,0.15)

=3C3*0.15^3(0.85)^0

=1*0.15^3*1

=0.03375

The rest of the exercises are similar.

You can attempt them and return for an answer check.

- math answer check -
**Nora 57**, Saturday, June 1, 2013 at 11:40pm#2 I get a different answer on this one and when I tried yours it was wrong, I got .0675 and when I worked (e). out I get a 0.6075 but that does not look right. (f) 2.25. I had got 2 answers right when I first done it and I did them all the same way and not sure how I am missing them still.

- math answer check -
**MathMate**, Sunday, June 2, 2013 at 10:32amI don't know to which question 0.0675 referred.

Note that:

nCr = n!/[(n-r)!(r!)]

For (e), we have

P(n=3,x=1,p=0.45)

=3C1*0.45^1*(1-0.45)^(3-1)

=3*0.45*0.55^2

=0.408375

(f) probabilities never exceed 1!

P(n=6,x=6,p=0.25)

=6C6*0.25^6*(1-0.25)^(6-6)

=1*0.25^6

=0.000244

- math answer check -
**Nora 57**, Thursday, June 6, 2013 at 7:11pmSorry , I worked them out and they are all wrong. I missed b, e, and f.