English

Calculate E~.E;,E~ from the Following: - Mathematics and Statistics

Advertisements
Advertisements

Question

Calculate `"e"_0^circ ,"e"_1^circ , "e"_2^circ` from the following: 

Age x 0 1 2
lx 1000 880 876
T - - 3323
Sum

Solution

We know that  `"e"_"x"^circ = "T"_"x"/"l"_"x"`

Age x lx Lx T
0 1000 940 5141
1 880 878 4201
2 876 - 33236

Lx = `("l"_"x" + "l"_("x" + 1))/2` , x = 0,1,2


L0 = `("l"_0 + "l"_1)/2 = (1000 + 880)/2 = 940`


L1 = `("l"_1 + "l"_2)/2 = (880 + 876)/2 = 878`

T2 = 3323 given

T1 = L1 + T2 = 878 + 3323 = 4201

T0 = L0 + T1 = 940 + 4201 = 5141


`"e"_0^circ = "T"_0/"l"_0 = 5141/1000 = 5.141`


`"e"_1^circ = "T"_1/"l"_1 = 4201/880 = 4.7739`


`"e"_2^circ = "T"_2/"l"_2 = 3323/876 = 3.7934`

shaalaa.com
  Is there an error in this question or solution?
2017-2018 (July) Set 1

APPEARS IN

RELATED QUESTIONS

From a lot of 30 bulbs which include 6 defectives, a sample of 4 bulbs is drawn at random with replacement. Find the probability distribution of the number of defective bulbs.


A random variable X has the following probability distribution.

X 0 1 2 3 4 5 6 7
P(X) 0 k 2k 2k 3k k2

2k2

7k2 + k

Determine

(i) k

(ii) P (X < 3)

(iii) P (X > 6)

(iv) P (0 < X < 3)


The random variable X has probability distribution P(X) of the following form, where k is some number:

`P(X = x) {(k, if x = 0),(2k, if x = 1),(3k, if x = 2),(0, "otherwise"):}`

  1. Determine the value of 'k'.
  2. Find P(X < 2), P(X ≥ 2), P(X ≤ 2).

Two dice are thrown simultaneously. If X denotes the number of sixes, find the expectation of X.


An urn contains 25 balls of which 10 balls bear a mark ‘X’ and the remaining 15 bear a mark ‘Y’. A ball is drawn at random from the urn, its mark is noted down and it is replaced. If 6 balls are drawn in this way, find the probability that

(i) all will bear ‘X’ mark.

(ii) not more than 2 will bear ‘Y’ mark.

(iii) at least one ball will bear ‘Y’ mark

(iv) the number of balls with ‘X’ mark and ‘Y’ mark will be equal.


Assume that the chances of the patient having a heart attack are 40%. It is also assumed that a meditation and yoga course reduce the risk of heart attack by 30% and prescription of certain drug reduces its chances by 25%. At a time a patient can choose any one of the two options with equal probabilities. It is given that after going through one of the two options the patient selected at random suffers a heart attack. Find the probability that the patient followed a course of meditation and yoga?


If the probability that a fluorescent light has a useful life of at least 800 hours is 0.9, find the probabilities that among 20 such lights at least 2 will not have a useful life of at least 800 hours. [Given : (0⋅9)19 = 0⋅1348]

 


A random variable X ~ N (0, 1). Find P(X > 0) and P(X < 0).


A bag contains 4 red and 6 black balls. Three balls are drawn at random. Find the probability distribution of the number of red balls.


The probability distribution of a random variable X is given below:

x 0 1 2 3
P(X) k
\[\frac{k}{2}\]
\[\frac{k}{4}\]
\[\frac{k}{8}\]

Determine P(X ≤ 2) and P(X > 2) .


Find the mean and standard deviation of each of the following probability distribution :

xi: 0 1 3 5
pi :  0.2 0.5 0.2 0.1

Find the mean and standard deviation of each of the following probability distribution :

xi :  -2 -1 0 1 2
pi :  0.1 0.2 0.4 0.2 0.1

Find the mean variance and standard deviation of the following probability distribution 

xi : a b
pi : p q
where p + q = 1 .

Two cards are drawn simultaneously from a pack of 52 cards. Compute the mean and standard deviation of the number of kings.


Write the values of 'a' for which the following distribution of probabilities becomes a probability distribution:

Xxi: -2 -1 0 1
P(Xxi) :
\[\frac{1 - a}{4}\]
 
\[\frac{1 + 2a}{4}\]
\[\frac{1 - 2a}{4}\]
\[\frac{1 + a}{4}\]

If the probability distribution of a random variable X is given by Write the value of k.

X = xi : 1 2 3 4
P (X = xi) : 2k 4k 3k k

 


If a random variable X has the following probability distribution:

X : 0 1 2 3 4 5 6 7 8
P (X) : a 3a 5a 7a 9a 11a 13a 15a 17a

then the value of a is


If X is a random-variable with probability distribution as given below:

X = xi : 0 1 2 3
P (X = xi) : k 3 k 3 k k

The value of k and its variance are



John and Mathew started a business with their capitals in the ratio 8 : 5. After 8 months, john added 25% of his earlier capital as further investment. At the same time, Mathew withdrew 20% of bis earlier capital. At the end of the year, they earned ₹ 52000 as profit. How should they divide the profit between them? 


The p.m.f. of a random variable X is
`"P"(x) = 1/5` , for x = I, 2, 3, 4, 5 
        = 0 , otherwise.
Find E(X).


Solve the following :

Identify the random variable as either discrete or continuous in each of the following. Write down the range of it.

20 white rats are available for an experiment. Twelve rats are male. Scientist randomly selects 5 rats number of female rats selected on a specific day


Determine whether each of the following is a probability distribution. Give reasons for your answer.

x 0 1 2 3 4
P(x) 0.1 0.5 0.2 –0.1 0.3

Find the probability distribution of the number of successes in two tosses of a die if success is defined as getting a number greater than 4.


A die is thrown 4 times. If ‘getting an odd number’ is a success, find the probability of 2 successes


10 balls are marked with digits 0 to 9. If four balls are selected with replacement. What is the probability that none is marked 0?


Defects on plywood sheet occur at random with the average of one defect per 50 sq.ft. Find the probability that such a sheet has:

  1. no defect
  2. at least one defect
    Use e−1 = 0.3678

Solve the following problem :

The probability that a component will survive a check test is 0.6. Find the probability that exactly 2 of the next 4 components tested survive.


Solve the following problem :

The probability that a machine will produce all bolts in a production run within the specification is 0.9. A sample of 3 machines is taken at random. Calculate the probability that all machines will produce all bolts in a production run within the specification.


Solve the following problem :

It is observed that it rains on 10 days out of 30 days. Find the probability that it rains on at most 2 days of a week.


A discrete random variable X has the probability distribution given as below:

X 0.5 1 1.5 2
P(X) k k2 2k2 k

Determine the mean of the distribution.


The probability distribution of a random variable X is given below:

X 0 1 2 3
P(X) k `"k"/2` `"k"/4` `"k"/8`

Determine the value of k.


A random variable x has to following probability distribution.

X 0 1 2 3 4 5 6 7
P(x) 0 k 2k 2k 3k k2 2k2 7k2 + k

Determine


Find the mean number of defective items in a sample of two items drawn one-by-one without replacement from an urn containing 6 items, which include 2 defective items. Assume that the items are identical in shape and size.


A person throws two fair dice. He wins ₹ 15 for throwing a doublet (same numbers on the two dice), wins ₹ 12 when the throw results in the sum of 9, and loses ₹ 6 for any other outcome on the throw. Then the expected gain/loss (in ₹) of the person is ______.


A large chain retailer purchases an electric device from the manufacturer. The manufacturer indicates that the defective rate of the device is 10%. The inspector of the retailer randomly selects 4 items from a shipment. Complete the following activity to find the probability that the inspector finds at most one defective item in the 4 selected items.

Solution:

Here, n = 4

p = probability of defective device = 10% = `10/100 = square`

∴ q = 1 - p = 1 - 0.1 = `square`

X ∼ B(4, 0.1)

 `P(X=x)=""^n"C"_x p^x q^(n-x)= ""^4"C"_x (0.1)^x (0.9)^(4 - x)`

P[At most one defective device] = P[X ≤ 1]

= P[X=0] + P[X=1]

= `square+square`

∴ P[X ≤ 1] = `square`


A primary school teacher wants to teach the concept of 'larger number' to the students of Class II. 

To teach this concept, he conducts an activity in his class. He asks the children to select two numbers from a set of numbers given as 2, 3, 4, 5 one after the other without replacement.

All the outcomes of this activity are tabulated in the form of ordered pairs given below:

  2 3 4 5
2 (2, 2) (2, 3) (2, 4)  
3 (3, 2) (3, 3)   (3, 5)
4 (4, 2)   (4, 4) (4, 5)
5   (5, 3) (5, 4) (5, 5)
  1. Complete the table given above.
  2. Find the total number of ordered pairs having one larger number.
  3. Let the random variable X denote the larger of two numbers in the ordered pair.
    Now, complete the probability distribution table for X given below.
    X 3 4 5
    P(X = x)      
  4. Find the value of P(X < 5)
  5. Calculate the expected value of the probability distribution.

Share
Notifications

Englishहिंदीमराठी


      Forgot password?
Use app×