Probability and Statistics - Online Test
Q1. The mean of 50 observations is 36, if two observations are 30 and 42 are deleted , then the mean of the remaining observations is
Answer : Option D
Explaination / Solution:
After deleting the observations 30 and 42
new sum
new mean
Q2. If two bats are picked at random, what is the probability that either both are red or both are white?
Answer : Option B
Explaination / Solution:
Probabilities if both either are Red or either are White
(3C2 + 4C2)/15C2 = (3 + 6)/105 → 3/35
Q3. If A and B are two mutually exclusive events, then P (A + B) is equal to
Answer : Option C
Explaination / Solution:
No Explaination.
Q4. For a bivariate frequency distribution then is
Answer : Option D
Explaination / Solution:
if then
Q5. If two bats are picked at random, what is the probability that none is white?
Answer : Option B
Explaination / Solution:
Probabilities if none are white
[11C2/15C2] = (55)/(105) = 11/21
Q6. If and are two independent events, then P is equal to
Answer : Option B
Explaination / Solution:
No Explaination.
Q7. A man travels at a speed of 20 km/hour and then return at a speed of 30 km/hour. His average speed of the whole journey is
Answer : Option A
Explaination / Solution:
average speed for whole journey is the H.M between 20 and 30
therefore, average speed km/hr
Q8. Direction: what will come in the place question mark in question given below?
10, 14, 18, 22, ?
Answer : Option D
Explaination / Solution:
Series Pattern is+4,
So next series 22+4 = 26
Q9. If E is an event, then 
is equal to
is equal to
Answer : Option D
Explaination / Solution:
No Explaination.
Q10. The S.D. of the first n natural numbers is
Answer : Option A
Explaination / Solution:
first n natural numbers are 1,2,3.....n
we know that,
sum of sqaure is
