The mean of a normal probability distribution is 500 and the standard deviation is 10. About 95 percent of the observations lie between what two values?
Answer(s): C
95% lie between plus and minus two standard deviations of the mean.
Which of the following is/are true?
Answer(s): A
If A and B are independent, P(A and B) = P(A).P(B) and vice versa. If A and B are mutually exclusive, P(A and B) = 0. Note that P(A or B) = P(A) + P(B) - P(A and B). Hence, if P(A and B) = P(A) + P(B), the P(A or B) = 0.This implies that neither A nor B can occur, giving P(A) = P(B) = 0.
Manufacturers were subdivided into groups by volume of sales. Those with more than $100 million in sales were classified as Class A large; those from $50 to $100 million as Class A medium size; and those between $25 and $50 million, and so on. Samples were then selected from each of these groups. What is this type of sampling called?
This is stratified random sampling. It is a method of selecting a random item from each section of the population. The randomness comes from the random selection from a particular section. Stratified refers to the division of the sections.
A study of 200 stamping firms revealed these incomes after taxes:Income After Taxes Number of FirmsUnder $1 million 102$1 million up to $20 million 61$20 million and more 37What is the probability that a particular firm selected has $1 million or more in income after taxes?
Answer(s): B
There are 200 firms altogether. 98 firms have more than a million in income. So 98/200 = 0.49
Fifteen accounting majors had an average grade of 90 on a finance exam. Seven marketing majors averaged 85, while ten finance majors averaged 93 on the same exam. What is the weighted mean for the 32 students taking the exam?
Answer(s): E
(15*90)+(7*85)+(10*93) = 2875. Therefore, the weighted mean will be 2875/32 = 89.84.
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