Chapter 6, Probability
The section between the mean (z = 0) and the point that is 1 standard deviation about the mean (z =1) contains_________% of the scores. a. 2.28 b. 13.59 c. 34.13 d. 0
34.13
A population of plant heights has a mean of μ = 13 and standard deviation of σ = 2. What is the probability of an individual plant having a height between 10 and 16? a. 13.36% b. 68.27% c. 86.64% d. 93.32%
86.64%
Given that p = 0.5, for which value of n will the bar graph for the corresponding binomial distribution look most like a normal distribution? a. n = 2 b. n = 10 c. n = 20 d. n =100
n =100
There are 12 blue marbles, 8 red marbles, and 20 green marbles ina jar. A marble is drawn from the jar and replaced. This is repeated 4 times, each time a green marble is drawn. On the fifth time, what is the probability of drawing a green marble? a. 0.5 b. 16/40 c. 19/40 d. 40%
0.5
For a normal distribution with μ = 2 and σ = 0.5, what is p(X < 1.7) + p(X < 2.3)? a. 0.2742 b. 0.4515 c. 0.7257 d. 1
1
Which of the following is not a valid probability? a. 0 b. 75% c. 1 d. 6/5
6/5
What is the probability of a z-score falling within one standard deviation of the mean in a normal distribution? a. 34.13% b. 65.87% c. 68.26% d. 95.44%
68.26%
Which of the following is equal to p(z > 2.00) in a normal distribution? I. p(z < -2.00) II. 1 - p(z < 2.00) III. ½ p(z > 1.00) a. I only b. I and II only c. II and III only d. I, II, and III
I and II only
For a normal distribution with a mean of 60 and a standard deviation of 5, what X values separate the middle 95% from the extreme values? a. X = 50.2 and X = 69.8 b. X = -1.96 and X = 1.96 c. X = 50 and X = 70 d. X = 55 and X = 65
X = 50.2 and X = 69.8
Find proportion of a normal distribution corresponding to each of the following sections: a. z > 0.80 b. z > -0.75 c. z > 1.00 d. z < 1.50 e. z < -0.50
a. 0.2119 b. 0.7734 c. 0.1587 d. 0.9332 e. 0.3085
Solve p(55<X<65)=? standard deviation= 10 mean (u) = 58
p(55<X<65)= p(-0.30<z<+0.70) = 0.1179 + 0.2580 = 0.3759
A population of birth weights has a mean of μ = 8.1, and a standard deviation of σ = 0.1. What is the probability of an individual weight being greater than 8.4? a. 99.87% b. 15.87% c. 2.28% d. 0.13%
0.13%
The population distribution of scores on a test is normal with μ = 40 and σ = 2. What is the probability of scoring less than a 38 on this test? a. 2.28% b. 13.59% c. 15.87% d. 34.13%
15.87%
What is the best explanation for why a normal distribution is only an approximation for a binomial distribution? a. Binomial values are discrete, and normal values are continuous. b. The means for the two distributions are different. c. The standard deviations for the two distributions are different. d. There are more outcomes in a normal distribution than in a binomial distribution.
Binomial values are discrete, and normal values are continuous.
The wingspan of a population of insects is normally distributed with μ = 42 and σ = 4. Which of the following is true? I. It is possible for an insect in this population to have a wingspan of 30. II. It is likely for an insect in this population to have a wingspan of 30. III. It is unlikely an insect in this population to have a wingspan of 30. a. I only b. I and II only c. I and III only d. I, II, and III
I and III only
Which of the following is a proper way to describe the probability of flipping heads on a fair coin? I. 1/2 II. 0.5 III. 50%
I, II, III
Which z-score mark separates the bottom 97.5% from the top 2.5% in a normal distribution? a. -1.96 b. -1 c. 1 d. 1.96
1.96
If a multiple choice quiz has 100 questions in which every question has 4 choices, what is the probability of getting fewer than 20 questions correct merely by guessing? a. 10% b. 25% c. 50% d. 90%
10%
The section between the mean (z = 1) and the point that is 2 standard deviation about the mean (z =2) contains_________% of the scores. a. 2.28 b. 13.59 c. 34.13 d. 0
13.59
What is the probability of a z-score being less than 2 standard deviations from the mean in a normal distribution? a. 95% b. More than 95% c. Less than 95% d. It depends on the mean.
More than 95%
Correctly order the following normal distribution following a z-score transformation: z-score: ___a____-3___b____-2___c____-1____d___0____e___+1___f____+2___g____+3____h_____ 34.13, 34.13, 13.59, 13.59, 2.28, 2.28,0.13,0.13
a. 0.13 b. 2.28 c. 13.59 d. 34.13 e. 34.13 f. 13.59 g. 2.28 h. 0.13
For a binomial distribution with p = 0.75 and n = 15, the probability of A occurring more than 10 times is about 68.65%. Using a normal distribution with μ = 11.25, σ = 1.667, and p(X >10.5) to approximate this probability gives 67.26%. Which of the following best explains the discrepancy between the actual value of 68.65% and the approximation of 67.26%? a. p(X > 10) should have been used instead of p(X > 10.5). b. p(X > 9.5) should have been used instead of p(X > 10.5). c. np is not high enough to achieve a closer approximation. d. nq is not high enough to achieve a closer approximation.
nq is not high enough to achieve a closer approximation.
The number of minutes spent reading in one day is normally distributed with a mean of μ = 23 and a standard deviation of σ = 5. How much time would you have to spend reading in a day to find yourself in the top 10% of readers? a. 16.6 b. 18 c. 28 d. 29.4
29.4
A population of insect weights is normal with a mean of μ = 16. If the probability of a weight falling between 10 and 22 is 95.44%, what is the standard deviation for this distribution? a. 1.5 b. 3 c. 6 d. 12
3
There are 5 cards face down on a table with the values 1, 2, 3, 4 and 5 written on them. James says the probability of randomly turning over an even number is 1/2 because there are two possibilities: even and odd. Which of the following statements is true? a. James is incorrect because the probabilities less than 1 are impossible. b. James is incorrect because the two possibilities of "even" and "odd" are not equally likely in this situation.
James is incorrect because the two possibilities of "even" and "odd" are not equally likely in this situation.
