" /> -->

#### Probability Distributions Book Back Questions

12th Standard EM

Reg.No. :
•
•
•
•
•
•

Time : 00:45:00 Hrs
Total Marks : 30
5 x 1 = 5
1. Normal distribution was invented by

(a)

Laplace

(b)

De-Moivre

(c)

Gauss

(d)

all the above

2. If Z is a standard normal variate, the proportion of items lying between Z = –0.5 and Z = –3.0 is

(a)

0.4987

(b)

0.1915

(c)

0.3072

(d)

0.3098

3. An experiment succeeds twice as often as it fails. The chance that in the next six trials, there shall be at least four successes is

(a)

240/729

(b)

489/729

(c)

496/729

(d)

251/729

4. If for a binomial distribution b(n,p) mean = 4 and variance = 4/3, the probability, P(X ≥ 5) is equal to :

(a)

(2/3)6

(b)

(2/3)5(1/3)

(c)

(1/3)6

(d)

4(2/3)6

5. The average percentage of failure in a certain examination is 40. The probability that out of a group of 6 candidates atleast 4 passed in the examination are:

(a)

0.5443

(b)

0.4543

(c)

0.5543

(d)

0.4573

6. 3 x 2 = 6
7. Define Binomial distribution.

8. Write down the conditions for which the binomial distribution can be used.

9. In a family of 3 children, what is the probability that there will be exactly 2 girls?

10. 3 x 3 = 9
11. In tossing of a five fair coin, find the chance of getting exactly 3 heads.

12. What is the probability of guessing correctly atleast six of the ten answers in a TRUE/FALSE objective test?

13. A pair of dice is thrown 4 times. If getting a doublet is considered a success, find the probability of 2 successes.

14. 2 x 5 = 10
15. When counting red blood cells, a square grid is used, over which a drop of blood is evenly distributed. Under the microscope an average of 8 erythrocytes are observed per single square. What is the probability that exactly 5 erythrocytes are found in one square?

16. Assuming one in 80 births is a case of twins, calculate the probability of 2 or more sets of twins on a day when 30 births occur.