A geologist has collected 10 specimens of basaltic rock and 10 specimens of granite. if the geologist instructs a laboratory assistant to randomly select 15 of the specimens for analysis, what is the pmf of the number of basalt specimens selected for analysis? what is the probability that all specimens of one of the two types of rock are selected for analysis?

Respuesta :

Part 1

Given that there are 10 specimens of basaltic rock and 10 specimens of granute, the probability of selecting a basaltic rock is 10 / 20 = 0.5 and the probability of selecting a granite is 10 / 20 = 0.5

Thus, the probability mass function of the number of basalt specimens selected for analysis is given by

[tex]f(x)=\left(^{10}_x\right)(0.5)^x(0.5)^{10-x}[/tex]



Part 2

The probability that all specimens of one of the two types of rock are selected for analysis is given by the sum of the probabilities that 10 basalt specimens and 5 igneous specimen is selected and the probabilities that 5 basalt specimens and 10 igneous specimen is selected.


The probability that 10 basalt specimens and 5 igneous specimen is selected is given by

[tex]\frac{\left(^{10}_{10}\right)\left(^{10}_{5}\right)}{\left(^{20}_{15}\right)}=\frac{252}{15,504}=0.01625[/tex]

The probability that 5 basalt specimens and 10 igneous specimen is selected is also given by

[tex]\frac{\left(^{10}_{10}\right)\left(^{10}_{5}\right)}{\left(^{20}_{15}\right)}=\frac{252}{15,504}=0.01625[/tex]


Therefore, the probability that all specimens of one of the two types of rock are selected for analysis is given by 2(0.01625) = 0.0325


The PMF of the number of selecting basalt specimen is [tex]\boxed{\bf P=^{10}C_{x}(0.5)^{x}(0.5)^{10-x}}[/tex] and the probability of selecting all specimen of one of two type of rocks is [tex]\boxed{\bf 0.0325}[/tex].

Further explanation:

Concept used:

The probability of an event [tex]E[/tex] can be calculated as follpws:

[tex]\boxed{P(E)=\dfrac{n(E)}{n(S)}}[/tex]

Here, [tex]n(E)[/tex] is the number of favorable outcomes in an event [tex]E[/tex] and [tex]n(S)[/tex] is the number of element in sample space [tex]S[/tex].

The probability mass function of getting exactly [tex]r[/tex] success in [tex]n[/tex] independent trial in an experiment can be expresses as follows:

[tex]\boxed{P=^nC_{r}p^{r}q^{n-r}}[/tex]

Here, [tex]p[/tex] is the success probability and [tex]q[/tex] is the failure probability of an event.

Calculation:

A geologist has collected [tex]10[/tex] specimens of ballistic rock and geologist collected [tex]10[/tex] specimens of granite.

The total number of specimens is [tex]20[/tex].

The sample space is the collection of all possible outcomes in an experiment.

Therefore, the total possible outcomes are [tex]20[/tex].

The probability of selecting ballistic rock can be calculated as follows:

[tex]\begin{aligned}P_{b}&=\dfrac{10}{20}\\&=\dfrac{1}{2}\\&=0.5\end{aligned}[/tex]

 

The probability of selecting granite can be calculated as follows:

[tex]\begin{aligned}P_{g}&=\dfrac{10}{20}\\&=\dfrac{1}{2}\\&=0.5\end{aligned}[/tex]

 

The PMF of selecting exactly [tex]x[/tex] basalt specimen for analysis can be calculated as follows:

[tex]\boxed{P=^{10}C_{x}(0.5)^{x}(0.5)^{10-x}}[/tex]

Consider [tex]A[/tex] as an event that all rocks are selecting from one rock and [tex]n(A)[/tex] as the number of favorable outcomes in an event [tex]A[/tex].

The number of favorable outcomes in an event [tex]A[/tex] can be calculated as follows:

[tex]\begin{aligned}n(A)&=\left(^{10}C_{10}\cdot ^{10}C_{5}\right)+\left(^{10}C_{10}\cdot ^{10}C_{5}\right)\\&=\left(\dfrac{10!}{10!\cdot (10-10)!}\cdot \dfrac{10!}{5!\cdot (10-5)!}\right)+\left(\dfrac{10!}{10!\cdot (10-10)!}\cdot \dfrac{10!}{5!\cdot (10-5)!}\right)\\&=\dfrac{10\cdot 9\cdot 8\cdot 7\cdot 6}{5\cdot 4\cdot 3\cdot 2\cdot 1}+\dfrac{10\cdot 9\cdot 8\cdot 7\cdot 6}{5\cdot 4\cdot 3\cdot 2\cdot 1}\\&=252+252\\&=504\end{aligned}[/tex]

 

The total possible outcomes of selecting [tex]15[/tex] rocks in [tex]20[/tex] rocks can be calculated as follows:

[tex]\begin{aligned}n(S)&=^{20}C_{15}\\&=\dfrac{20!}{15!\cdot (20-15)!}\\&=\dfrac{20\cdot 19\cdot 18\cdot 17\cdot 16\cdot 15!}{15!\cdot 5!}\\&=\dfrac{20\cdot 19\cdot 18\cdot 17\cdot 16}{5\cdot 4\cdot 3\cdot 2\cdot 1}\\&=19\cdot 3\cdot 17\cdot 16\\&=15504\end{aligned}[/tex]

The probability [tex]P(A)[/tex] of selecting all specimen of one of two type of rocks can be calculated as follows:

[tex]\begin{aligned}P(A)&=\dfrac{504}{15504}\\&=0.0325\end{aligned}[/tex]    

Thus, the probability that all specimens of one of the two types of rock are selected for analysis is [tex]\boxed{\bf 0.0325}[/tex].

Learn more:

1. Learn more about functions https://brainly.com/question/2142762

2. Learn more about numbers https://brainly.com/question/1852063

Answer details:

Grade: College school

Subject: Mathematics

Chapter: Probability

Keywords: Basalt specimen, geologist, rock, granite, PMF, probability mass function, exactly, probability, possible outcomes, favorable, failure success,  , event, experiment, trial, P=n(E)/n(S).